To title page of Tertiary Marine Pelecypods of California and Baja California
[Please cite as follows: Moore, E.J., 2002, Family Mactridae, in Tertiary marine pelecypods of California and Baja California, Chapter F: http://www.cmug.com/~chintimp/Mactridae.htm, 33 p., 9 pl.]
Family MACTRIDAE
Subfamily MACTRINAE
According to Saul (1991, p. 17) "Hinge teeth suggest that recent northeast [Pacific] mactrids should be allocated to six supraspecific taxa: Tresus, Mactromeris, Mactrotoma, Microtoma, Simomactra, and Raeta. Tresus and Mactromeris are cool water mactrids with a long geological history in the north Pacific. The other four are warm water mactrids: Macrotoma and Simomactra have a longer Pacific basin geological record than Micromactra or Raeta, but these latter two have a longer Atlantic basin record."
Coan, Scott, and Bernard (2000, p. 457) said that "***there are no species [living] in the eastern Pacific closely similar to the European type species of either Mactra or Spisula, which are both small, inflated, with small pallial sinuses. True Spisula***also have strongly grooved, lateral teeth."
Genus MACTRA Linné 1767
"Trigonal to oval, somewhat inflated, subequilateral; lunule and escutcheon delimited; ligament separated from resilium by shelly lamina; lateral teeth smooth; pallial sinus oval." (Moore, 1969, p. N595)
Geographic range.--Cosmopolitan.
Geologic range.--Eocene to Holocene.
Mactra diegoana Conrad, nomen dubium
Mactra diegoana Conrad, 1855, p. 14; 1857, pl. 5, fig. 45; not pl. 4, fig. 35 as stated by Conrad (Keen and Bentson, 1944, p. 64).
Original description.--"Triangular ventricose, inequilateral, anterior side oblique, rectilinear; umbonal slope carinated and nearly terminal; basal margin profoundly and regularly rounded."
Holotype.--Missing and presumed lost.
Type locality.--San Diego, Calif.
Occurrence in California.--Occurrence not known.
Comments.--It is probably best to consider Mactra diegoana Conrad a nomen dubium.
Genus PSEUDOCARDIUM Gabb
"Shell solid, rounded-trigonal; hinge with long substriate or pitted laterals; pallial sinus short, rounded." (Moore, 1969, p. N601)
"Pseudocardium appears to be extinct in the eastern Pacific but is known in northern Japan where it is represented by 'Mactra' sachalinensis Schrenck.***Some specimens of Pseudocardium, both living and fossil, have a small ridge dividing the two parts of the ligament, so that Pseudocardium might be cited as a connecting form between Mactra and Spisula. Some specimens of typical Spisula, however, have at least a suggestion of this ridge, and Pseudocardium is probably more closely related to Spisula than to Mactra." (Woodring, 1940, p. 94)
Geographic range.--Western North America and eastern Asia.
Geologic range.--Eocene to Pliocene.
Pseudocardium meganosensis (Clark and Woodford)
Plate 5, figures 1, 2, 5; Plate 5; Plate 5 caption
Spisula meganosensis Clark and Woodford, 1927, p. 104-105, pl. 18, figs. 11-13.
Original description.--"Shell trigonal, adult rather large and heavy; moderately turned; beaks prominent, strongly inturned, and prosogyrous; anterior dorsal margin long, almost straight; posterior dorsal margin gently convex; anterior end narrow and bluntly pointed; posterior end curving down to an obscure angle with the ventral edge which is regularly rounded. A very prominent ridge extends from the beaks to the posterior extremity, setting off from the rest of the shell the steep posterior dorsal slope. On this steep slope, about midway, there is another much fainter ridge which is roughly parallel to the first mentioned. A third, somewhat obscure ridge extends from the beaks to the anteroventral angle setting off an anterior dorsal marginal area, which is slightly concave from the main surface of the shell. Surface smooth except for rather coarse, somewhat irregular incremental lines. Resilifer elongate, rather narrow, directed backwards almost parallel with the posterior dorsal margin. A rather heavy, short, anterior lateral in the left valve fits between equally heavy laminae in the right; the posterior lateral of the left valve and the clasping laminae of the right are longer and more slender than those anterior. Dimensions--Type: Length 55 mm., height 44 mm., thickness of one valve 15 mm. Paratype 31339: Length 64 mm., height 53 mm., thickness of a single valve 17 mm. (Largest specimen found)."
Holotype.--UCMP 31338.
Type locality.--UC 3579. Contra Costa County, Calif. Meganos Formation, Paleocene.
Comparison.--"Spisula meganosensis has a slight superficial resemblance to S. (Cymbophora) asburnerii (Gabb)***S. ashburnerii has a much higher and narrower beak than any of our specimens, the general outline is different and the hinge is very different.
"S. meganosensis is close to S. merriami Packard in outline, but differs in size of adult, thickness of shell, character of sculpturing and of hinge plate.
"Another species sometimes found and possibly characteristic of the Meganos is Spisula tejonensis Packard. S. meganosensis differs from S. tejonensis in its less elongate form, thicker shell, and larger size of the adult. S. meganosensis is similar to S. packardi Dickerson, described from the lower Oligocene of Washington, from which it differs in that it is proportionately shorter, the anterior end is not so acutely pointed, and the laterals are shorter and heavier." (Clark and Woodford, 1927, p. 105)
Occurrence in California.--Paleocene: Meganos Formation (Clark and Woodford, 1927).
Pseudocardium packardi (Dickerson)
Spisula packardi Dickerson, 1917, p. 169, pl. 28, figs. 5a, 5b. Wagner and Schilling, 1923, p. 243-244. Weaver, 1943, p. 231, pl. 54, figs. 2, 4. Not Kleinpell and Weaver, 1963, p. 206, pl. 37, figs. 5, 6.
Mactra packardi (Dickerson). Clark and Anderson, 1938, p. p. 948, pl. 2, figs. 6, 7.
Original description.--"Shell large trigonal, equivalve, nearly equilateral, ventricose, ornamented by numerous fine concentric ridges which are more pronounced and more numerous on the anterior dorsal area than upon other portions of the shell; beaks moderately prominent; anterior dorsal area limited by a distinct ridge extending from the umbo to the anterior extremity; the margin of this area slightly curved; posterior dorsal slope slightly convex, limited by an indistinct ridge which extends from the beak to the base of the shell; anterior extremity more sharply pointed than the posterior; base very broadly rounded; hinge plate fairly broad; chondophore oblique, shallow, apically roofed by a broad flat spur; left cardinal prominent, high, arms broad, extending from the dorsal to the ventral margin of the plate; ventral sinus, narrow, deep; right cardinal with a prominent anterior arm and with a well developed, but very thin, posterior arm; laminae long, fairly distant from beaks; anterior lateral formed from the margin of the plate, top acute; posterior lateral also with acute top, dorsal and ventral slopes nearly equal; anterior ventral lamina formed from upturned edge of the hinge plate not confluent with the anterior dorsal cardinal arm.
Holotype.--CAS 395.
Type locality.--"Near Vader, Lewis County, Washington, on east bank of the Cowlitz River, just back of the Greeco ranch house, about four miles [6 km] east of Vader." Gries Ranch Formation, Eocene and Oligocene.
Comparison.--"This species has the same general outline as S. merriami Packard, but its sculpturing on the anterior dorsal area is different, its posterior less sharply truncated and the laminae more divergent." (Dickerson, 1917, p. 169)
Occurrence in California.--Eocene and Oligocene: San Emigdio (Wagner and Schilling, 1923) and Wheatland (Clark and Anderson, 1938) Formations.
Pseudocardium panzanum (Loel and Corey)
Plate 5, figure 13; Plate 5; Plate 5 caption
Mulinia (=Pseudocardium) panzana Loel and Corey, 1932, p. 232-234, pl. 45, figs. 8, 9.
Pseudocardium panzanum (Loel and Corey). Keen and Bentson, 1944, p. 70. Adegoke, 1969, p. 118-119.
Original description.--"Shell large, fairly ventricose, nearly equilateral; umbones inflate[d], high, separated from main outline of margins, medially located; valves equal; dorsal margins gently arched, nearly horizontal, anterior dorsal margin nearly straight; anterior extremity broadly rounded with a suggestion of truncation, posterior dorsal margin gently convex, posterior extremity evenly round, joining broadly arched ventral margin in a sharp turn; a constriction and slight sulcus just before posterior extremity gives a suggestion of an umbonal ridge, beaks, incurved, not prominent, proximate; surface smooth except near ventral margin where incremental lines become prominent. The hinge of the type specimen is obscured; that of the right valve figured as paratype is narrow, long, not heavy, broadly arched; condrophore small, deep. Dentition is delicate, elongate."
Holotype.--UCMP 31792.
Type locality.--"Univ. Calif. loc. A505, from top of white sandstone reef, Vaqueros-Temblor transition zone, head of Anderson's Creek (west branch), which is tributary to San Juan River, edge of Carrizo Plains, La Panza Mountains, eastern San Luis Obispo County", Calif.
Comparison.--"The form is constant as described and differs from Mulinia densata Conrad (Packard, 1916) mainly in these characters: 1, roundness and highness of anterior portion; 2, anterior dorsal margin nearly horizontal; 3, constantly less convex and umbones less promenent, less continuous with shell body; 4, more elongate; 5, smooth surface (constant)." (Loel and Corey, 1932, p. 233)
Occurrence in California.--Oligocene and Miocene: Temblor (Adegoke, 1969) and Vaqueros (Loel and Corey, 1932) Formations; Miocene: Topanga Formation (Suski, written commun., 1978).
Pseudocardium densatum densatum (Conrad)
Plate 5, figures 6, 7; Plate 5; Plate 5 caption
Mulinia densata Conrad, 1856, p. 313; 1857, p. 71, pl. 3, fig. 12. Arnold, 1910, p. 140, 148, pl. 17, figs. 3, 4; pl. 21, fig.3. Clark, 1915, pl. 60, fig. 5. Packard, 1916, p. 304-305, pls. 29-33.
Mactra (Pseudocardium) densata (Conrad). Grant and Gale, 1931, p. 403-404.
Pseudocardium densatum (Conrad). Woodring and others, 1940, p. 93, pl. 24, figs. 14, 19; pl. 29, fig. 16; pl. 30, figs. 1-8; pl. 37, figs. 3-10. Adegoke, 1969, p. 119.
Cardium gabbii Rémond, 1863, p. 13.
Mulinia oregonensis Dall, 1909, p. 132, pl. 9, figs. 2, 3;pl. 13, fig. 5.
Pseudocardium oregonense (Dall). Weaver, 1943, p. 246, pl. 58, figs. 1, 5.
Original description.--"Subovate, ventricose, thick, very inequilateral; posterior side very short comparatively, contracted; extremity subtruncated, much above the line of the base; posterior basal margin very oblique and contracted; anterior end obliquely truncated; anterior basal margin rounded; summits prominent, distant; external teeth very robust and prominent; inner margin entire."
Holotype.--Missing and presumed lost (Moore, 1963, p. 110); syntypes of oregonensis USNM 153927 and 153977; holotype of gabbi ANSP 4493 (Stewart, 1930, p.278).
Type locality.--Near Santa Barbara, Calif. Monterey Formation(?), Miocene(?); of oregonensis, Fossil Point, Coos Bay, Oregon. Empire Formation, Miocene; of gabbi, vicinity Kirker's Pass, [Contra Costa County], Calif. San Pablo Formation, Miocene.
Supplementary description.--"The hinge plate of Mulinia densata is rather wide; chondophore deep; roofed apically and overhung by a lamella in the left valve; the left cardinal prominent, often heavy, the arms of equal width, and often fused together in the Pseudocardium forms, producing a triangular block-tooth and varying in this respect to a condition where the arms are clearly defined; the arms of the cardinal reach ventrally nearly across the hinge plate; the anterior arm of the right cardinal is more prominent than the posterior one; laterals of unequal length; distant from the beaks, being relatively short and heavy in the more ventricose forms; anterior lateral nearly in alignment with the cardinal arm, but distant from that tooth; laminae heavy, the anterior ventral one is in line with the cardinal arm; dorsal laminae small, arising from the dorsal margin of the shell. Pallial sinus shallow, broadly rounded." (Packard, 1916, p. 306)
Comparison.--"Mulinia densata is separable from M. pabloensis by the lack of striations on the lateral teeth; from M. alta by its much heavier left cardinal and wider hinge plate; and from M. undilifera by its narrower hinge plate and more delicate teeth." (Packard, 1916, p. 306)
Occurrence in California.--Oligocene and Miocene: Temblor Formation (Adegoke, 1969); Miocene: Monterey Group (Packard, 1916) and Neroly Sandstone, San Pablo Group (Weaver, 1949); Miocene and Pliocene: Etchegoin Formation (Packard, 1916; Woodring and others, 1940; Adegoke, 1969); Pliocene: Cascajo Conglomerate Member, San Joaquin Formation (Adegoke, 1969).
Pseudocardium densatum minor (Arnold)
Plate 5, figure 4; Plate 5; Plate 5 caption
Mulinia densata var. minor Arnold, 1910, p. 54, pl. 5, fig. 6. Packard, 1916, p. 307.
Mactra (Pseudocardium) densata (Conrad). Grant and Gale, 1931, p. 403-404, in part.
Pseudocardium densatum minor Arnold. Stewart, 1946, pl. 17, fig. 6.
Pseudocardium densatum (Conrad) minor (Arnold). Adegoke, 1969, p. 119.
Original description.--"This variety is characterized by its smaller size, and more inequilateral form than the typical M. densata Conrad. (Pacific Railroad Repts., vol. 6, p. 71, pl. 3, fig. 12.) The typical M. densata is found most abundantly in the upper Miocene; var. minor is commoner in the lower Miocene (Vaqueros), although specimens indistinguishable from the Vaqueros forms are found in the Etchegoin. Mulinia densata is also known as Pseudocardium gabbi Rémond."
Holotype.--USNM 165601.
Type locality.--USGS 4777. Jasper Creek, above Ramirez place at forks of Jacalitos Creek, [W 1/2, Sec. 23, T. 22 S., R. 15 E., Fresno County], Calif. Temblor Formation, Oligocene and Miocene.
Supplementary description.--This variety [densatum minor] is characterized by its smaller size, and its more inequilateral form than the typical M. densata. Its hinge is unknown." (Packard, 1916, p. 307)
Occurrence in California.--Oligocene and Miocene: Temblor (Keen and Bentson, 1944; Stewart, 1946; Adegoke, 1969) and Vaqueros (Arnold, 1910) Formations; Miocene and Pliocene: Etchegoin Formation (Arnold, 1910; Packard, 1916).
Pseudocardium pabloensis (Packard)
Plate 5, figure 3; Plate 5; Plate 5 caption
Mulinia pabloensis Packard in Clark, 1915, pl. 60, figs. 1, 2, 7. Packard,1916, p. 309-31l, pl. 34, figs. 4a, 4b.
Mulinea pabloensis Packard. Clark, 1929, pl. 33, fig. 2.
Pseudocardium pabloensis (Packard). Hall, 1958, p. 53, pl. 4, fig. 2. Adegoke, 1969, p. 119.
Original description.--"Shell rather ventricose, nearly equilateral, umbones usually posterior to the middle of the shell; anterior dorsal edge nearly straight, excavated in front of the beaks; anterior extremity rounded to subtruncate; posterior dorsal edge slightly convex, extremity strongly truncated; some specimens show a posterior umbonal ridge, which is imperfectly seen in the type; base broadly arcuate. Surface roughened by numerous irregular lines of growth. Pallial sinus shallow; other muscle scars deeply impressed. The hinge of the type lacks the posterior laminae and the posterior arm of the cardinal. Hinge plate rather heavy, chondophore relatively shallow, roofed; right cardinal with a small anterior arm which is closely appressed to the dorsal margin of the shell; anterior laminae long, strongly striated on their inner sides, the dorsal one being nearly as long as the ventral one, and arising as a long thin tooth, from the hinge plate to a height greater than that of the adjacent shell margin. In one specimen the ventral lamina is rather heavy and distinctly striated, not confluent with the anterior arm of the cardinal. The cotype shows the left valve with a rather small but prominent cardinal and large striated laterals, which are distant from the umbones, the anterior one not reaching to the cardinal arm. The dimensions of the type are: height, 43 mm., convexity, 18 mm.. Those of the cotype are: length, 54 mm., height, 48 mm., convexity, 36 mm."
Holotype.--UCMP 11442.
Type locality.--UC 1946. "About 150 feet [45 m] slope distance up the south-west side of the highest hill north-east of Joe Mendosa's house, which is about one-half mile [0.8 km] south-west of Shell Ridge, Concord Sheet, Contra Costa County, California."
Comparison.--"This species is extremely variable in general shape, paralleling in many respects the forms assumed by Mulinia [Pseudocardium] densata. It differs from all mulinoid species of the Coast region in the striated character of its laterals and laminae." (Packard, 1916)
Occurrence in California.--Oligocene and Miocene: Temblor Formation (Adegoke, 1969); Miocene: Monterey Group (Packard, 1916), Neroly Sandstone, San Pablo Group (Weaver, 1949), and Santa Margarita Formation (Adegoke, 1969).
Genus PSEUDOCARDIUM?
Pseudocardium? orthomorpha (Grant and Gale)
Plate 5, figure 8; Plate 5; Plate 5 caption
Mactra (Mactra) orthomorpha Grant and Gale, 193l, p. 391, pl. 23, figs. 2a-c, 6, 7.
Original description.--"Shell ovate-subtrigonal, moderately ventricose, of moderate thickness; umbones rather full, coming to a blunt point at the dorsal margins of the valves; surface of valves marked with fine, low, irregular growth lines and a low angulation running from the umbo to the posterior ventral margin; hinge normal, chondrophore prominent, wide, overhung by a spur, lateral laminae rather long, well-developed, in the right valve a second set attached to the dorsal margin of the valve. Length, about 39 mm.; height, about 32 mm.; convexity of one valve, about 12 mm."
Holotype.--SDNM 193.
Type locality.--"Federal Exploration Company's well, Kinsella No. 1, depth 2794 feet [852 m], Sec. 15, R. 22, R. 24, near Tipton, Tulare County, California." Etchegoin Formation, Miocene and Pliocene.
Comparison.--"'Mulinia' pabloensis Packard***may be related to this new species [orthomorpha]. Packard's species is larger, has broader umbones and heavier laterals, which have transverse striations.
"Mactra orthomorpha is entirely different from Mactra californica Conrad, which is a relatively much longer and less ventricose shell, with shorter lateral teeth. Conrad's species is also thinner shelled." (Grant and Gale, 1931, p. 391)
Occurrence in California.--Miocene and Pliocene: Etchegoin Formation (Grant and Gale, 1931).
Genus MACTROMERIS Conrad, 1868
Shell large, subequilateral, inflated. Periostracum usually fibrous. Two cardinals in each valve forming a wide inverted V. In left valve the anterior cardinal is bifid, posterior slender and very near posterior side of the bifid tooth. (L.R. Saul, written commun., 1992)
Geographic range.--Western North America, Japan, northern Atlantic.
Geologic range.--Miocene to Holocene.
Mactromeris capayana (Vokes)
Plate 6, figures 1, 2; Plate 6; Plate 6 caption
Spisula capayana Vokes, 1939, p. 97-98, pl. 15, figs. 9-11.
Original description.--"Shell small, ovate, produced anteriorly; umbos posterior to median line, inflated; anterior dorsal margin convex; anterior margin rounded, the ventral margin broadly and regularly rounded, the posterior ventral margin angulate; posterior dorsal margin broadly convex; a sharp, almost straight posterior umbonal ridge extending to the posterior ventral margin, and a poorly developed anterior umbonal ridge extending in a curve to the anterior end; center of the valve smooth except for lines of growth, the anterior and posterior dorsal slopes with prominent concentric ribbing extending to but not crossing the umbonal grooves, the ribs being finer and more numerous upon the anterior dorsal slope than upon the posterior; hinge not seen."
Syntypes.--UCMP 15714, 15715.
Type locality.--UC 1817. Fresno Coutny, Calif. Cerros Shale Member, Lodo Formation, Paleocene.
Comparison.--"S. capayana may be distinguished from S. bisculpturata Anderson & Hanna***, which it most closely resembles, in having more inflated and prominent umbos, a more rounded anterior margin, and more convex anterior and posterior dorsal margins, giving the shell a more ovate appearance, in lacking the shallow depression immediately following the anterior umbonal ridge, and in the absence of the bisculptate condition of the sculpturing upon the anterior dorsal slope. The new species is less equilateral than S. merriami Packard, more broadly rounded anteriorly, the posterior umbonal ridge is more sharply developed, and the concentric sculpturing is never present upon the center of the valve." (Vokes, 1939, p. 98)
Comments.--The specimen called a "syntype" by Vokes (1939, p. 97) and bearing UCMP number 11715, seems to be a tellinid (pl. 6, fig. 1) and presumably was misnumbered.
Occurrence in California.--Paleocene: Cerros Shale Member, Lodo Formation (Vokes, 1938).
Mactromeris acutirostrata (Packard)
Plate 6, figures 5, 7; Plate 6; Plate 6 caption
Spisula acutirostrata Packard, 1916, p. 295-296, text figs. 2a, b.
Original description--"Shell medium sized, slightly ventricose, trigonal in outline; inequilateral; sculptured by indistinct incremental lines of growth; beaks prominent, strongly incurved and acutely pointed; posterior dorsal margin somewhat convex; anterior margin also slightly convex. Anterior extremity of the cotype produced and slightly truncated, while the posterior end is more evenly rounded; ventral margin arcuate. Escutcheon of the type specimen impressed and broad; posterior dorsal area limited by a prominent angulation or ridge which extends from the umbo to the posterior extremity. Hinge plate rather wide; chondophore deep, quite broad; left cardinal broken, but it was apparently low, heavy and not extending to the ventral margin of the plate. No accessories nor spur observable. Anterior lateral low, long; posterior lateral also rather low. Hinge of right valve unknown. The dimensions of the type are: height, 55 mm., length, 53 mm., convexity, 17 mm."
Holotype.--UCMP 33377.
Type locality.--UC 463. "SE 1/4 of NW 1/4 of Sec. 32, T 10 N, R 20 W. On a branch canon of Salt Creek, 150 feet [45 m] above the bottom. Mount Pinos sheet, California." Kern County, Calif. Tejon Formation, Eocene.
Supplementary description.--"This is the largest of the known West Coast Eocene species. It is characterized by its pronounced posterior ridge, its escutcheon and its small heavy cardinal." (Packard, 1916, p. 295)
Comparison.--"It [acutirostrata] differs from S. merriami, which it superficially resembles, in its more massive cardinal, more prominent posterior ridge and in the lack of pronounced ribs." (Packard, 1916, p. 295)
Geologic range.--Eocene.
Occurrence in California.--Eocene: Tejon Formation (Packard, 1916).
Mactromeris bisculpturata (Anderson and Hanna)
Plate 6, figure 4; Plate 6; Plate 6 caption
Mactra ashburnerii Gabb, 1864, p. 153, in part, Tertiary specimens only.
Cymbophora asburnerii Gabb, 1869, p. 181, in part, Tertiary specimens only. Not Cymbophora ashburnerii Gabb of Stewart, 1930.
Spisula bisculpturata Anderson and Hanna, p. 149-150, pl. 3, fig. 7. Weaver, 1942, p. 234-235, pl. 54, fig. 7.
Original description.--"Shell small, trigonal, produced posteriorly, moderately inflated; anterior dorsal slope very convex, bounded by a distinct ridge extending from the beak to the basal margin in a gentle curve; ridge immediately followed by a shallow depression; posterior dorsal slope straight, bounded by a ridge similar to that of the anterior slope, but concave when compared to a vertical line from the beak to the margin of the shell; base of the shell forming the arc of a circle, the center of which is 5 mm. below the apex. Surface marked by fine irregular lines of growth, or quite smooth except at the ends; anterior and dorsal slopes marked by distinct concentric ridges; the anterior slope bisculpturate, bisected by a line extending from the beak to the margin, the anterior half having distinct concentric ridges, the remainder showing chiefly radial sculpture. length of type, 26.2 mm.; altitude, 19.0 mm.; ratio nearly 4:3; thickness of single valve, 6.0 mm."
Holotype.--CAS 794 (CAS 244.04, new number).
Type locality.--CAS 244. "Live Oak Creek, Kern County, California." Tejon Formation, Eocene.
Comparison.--"Compared to S. merriami this species [bisculpturata] differs in some important particulars: the surface of S. merriami is ornamented with decided, or coarse concentric ridges, very regular in character, with no depression behind the anterior umbonal ridge; valves more nearly equilateral; the basal margin curved on a longer radius; posterior dorsal slope slightly convex. Notwithstanding these differences the new species resembles S. merriami more closely than any other." (Anderson and Hanna, 1925)
Occurrence in California.--Eocene: Tejon Formation (Anderson and Hanna, 1925).
Mactromeris tejonensis (Packard)
Plate 6, figure 3; Plate 6; Plate 6 caption
Spisula tejonensis Packard, 1916, p. 303-304, pl. 27, fig. 5. Clark and Woodford, 1927, p. 105, pl. 18, fig. 14.
Original description.--"Shell small, elongate, equivalve and nearly equilateral; umbones not prominent, adjacent; anterior dorsal edge slightly concave immediately under the beaks, but then becoming straighter until the rather arcuate anterior extremity is reached; posterior dorsal edge slightly convex; posterior extremity a little more rounded than the anterior; base broadly and evenly rounded; dorsal area limited by an indistinct umbonal ridge, extending from the beaks to the posterior extremity of the shell; this posterior dorsal area is marked by fine regularly disposed concentric ridges, which do not typically extend beyond the slightly carinated umbonal ridge. Interior unknown. The dimensions of the type are: length, 22.5 mm., height, 16.5 mm., convexity, 6 mm."
Holotype.--UCMP 11488.
Type locality.--UC 785. "Vicinity of Lower Lake, Lake County, Tejon Group. NW 1/4 of SE 1/4 of Sec. 6, T13 N, R 6 W, in a west gully near hill top, California. Elevation 1750 feet [535 m]." Tejon Formation, Eocene.
Comparison.--"This species [tejonensis] is distinguished from S. merriami by its less ventricose and more elongate shape, together with its less pronounced concentric sculpture." (Packard, 1916, p. 303)
Occurrence in California.--Paleocene: Meganos Formation (Clark and Woodford, 1917; Anderson and Hanna, 1925); Eocene: Tejon Formation(?) (Packard, 1916).
Mactromeris ramonensis ramonensis (Packard)
Plate 6, figures 13-15; Plate 6; Plate 6 caption
Spisula ramonensis Packard in Clark, 1915, p. 15. Clark, 1918, p. 1918, p. 158, pl. 9, fig. 4. Clark, 1932, p. 820, pl. 14, figs. 1, 4, 5; pl. 19, fig. 3.
Spisula albaria (Conrad) var. ramonensis Packard, 1916, p. 291-292, pl. 23, fig. 5; pl. 25, figs. 1, 2.
Original description.--"Shell medium-sized, inequilateral, somewhat compressed; height nearly equal to that of the length; umbones rather prominent, sharply pointed; shell smooth except for an occasional heavy incremental line of growth; anterior dorsal area excavated below the umbones; anterior dorsal edge straight; posterior dorsal edge convex; sloping regularly to the broadly rounded extremity; base arcuate. Hinge plate wide, chondophore deep, not roofed; left cardinal prominent, extending from the dorsal to the ventral margin of the plate; arms of equal length, heavy, the posterior one bearing an indistinct lamella; ventral sinus narrow; laterals long, the anterior one arising from the ventral edge of the plate; it is nearly flat-topped, and is not in alignment with, nor reaching to the anterior arm of the cardinal. The pallial sinus, as well as the hinge of the right valve is unknown, The dimensions of the type are: Height, 54.5 mm., convexity, 17.5 mm. Those of the cotype are: length, 60 mm., height, 50 mm., convexity, 13 mm."
Holotype.--UCMP 11118.
Type locality.--UC 1687. "To the north of the road leading to Tice Valley, west of the first 'a' in 'San Ramon', Concord sheet, Contra Costa County, California." San Ramon Formation, Miocene(?).
Comparison.--"It [ramonensis] differs from Conrad's species [albaria] in that the hinge plate is relatively wider, the left cardinal is heavier and the laterals are longer and more distant from the cardinal arm." (Packard, 1916, p. 292)
Occurrence in California.--Eocene and Oligocene: San Emigdio (De Lise, 1967) and San Lorenzo (Clark,1918) Formations; Oligocene: Wygal Sandstone Member, Temblor Formation (Addicott, 1973); Miocene(?): San Ramon Formation (Clark, 1918; Weaver, 1949).
Mactromeris ramonensis attenuata (Clark)
Plate 6, figures 8, 10, 11; Plate 6; Plate 6 caption
Spisula ramonensis attenuata Clark, 1918, p. 158-159, pl. 9, fig. 6. Clark, 1929, pl. 15, fig. 3.
Original description.--"Shell medium in size, longer than high, equivalved, inequilateral; beaks fairly conspicuous, strongly inturned, anterior to middle. Anterior dorsal slope long and nearly straight; posterior dorsal slope fairly steep and slightly convex. Anterior end strongly produced, rather attenuately rounded; posterior end broadly rounded. Surface smooth except for medium fine, incremental lines. Extending from the beak to the ventral side of the posterior end is a well-marked ridge, posterior to which the surface is depressed rather strongly."
Holotype.--UMCP 11119.
Type locality.--UC 1167. "On first ridge N of Sobrante Ridge, Long. 122°12'37", Lat. 37°56'17", Contra Costa Co." Calif. San Ramon Formation, Miocene(?). (Keen and Bentson, 1944, p. 109)
Comparison.--"The chief basis for separating it [attenuata] from S. ramonensis, found in the same horizon, is the more strongly produced anterior end and the more prominent posterior ridge." (Clark, 1918, p. 159)
Occurrence in California.--Miocene(?): San Ramon Formation (Clark, 1918; Weaver, 1949).
Mactromeris rushi (Wagner and Schilling)
Plate 6, figures 6, 9; Plate 6; Plate 6 caption
Spisula rushi Wagner and Schilling, 1923, p. 256, pl. 47, fig. 2.
Original description.--"Shell medium sized; thin; equivalve; inequilateral; height about 5/7 the length; beaks prosogyrous and considerably anterior to the center of the shell; faint lunule-like area; umbonal area wide; anterior dorsal margin straight or slightly concave; posterior dorsal margin slightly convex; elongate escutcheonal area on depressed posterior dorsal margin apparently limited by faint lines; anterior and posterior extremities broadly rounded; ventral edge gently arcuate; shell covered by rather fine incremental lines; hinge unknown. Dimensions: length, 67 mm.; height, 52 mm.; convexity, 16 mm."
Holotype.--UCMP 11422.
Type locality.--UC 3179. East side of San Emgidio Canyon, NW 1/4, sec. 16, T. 10 N., R. 21 W., SB, Mt. Pinos Quad., Kern Co., Calif. San Emigdio Formation, Eocene and Oligocene (Keen and Bentson, 1944).
Comparison.--"This species [rushi] is somewhat similar to S. occidentalis (Gabb) but is readily distinguished from it by the lack of subtruncation at the posterior end which is so pronounced on the latter. The posterior dorsal margin of S. rushi has a steeper slope and the rounding at the posterior extremity is not so gentle. There is also a considerable difference in the general outline and proportions." (Wagner and Schilling, 1923, p. 256)
Occurrence in California.--Eocene and Oligocene: San Emigdio Formation (De Lise, 1967); Oligocene: Pleito Formation (Wagner and Schilling, 1923).
Mactromeris muliniaformis (Wagner and Schilling)
Plate 7, figures 5, 6; Plate 7; Plate 7 caption
Spisula muliniaformis Wagner and Schilling, 1923, p. 257, pl. 48, figs. 1, 2.
Original description.--"Shell very large; thick; trigonal in outline; nearly equilateral; slightly longer than high; umbones prominent; area below and anterior to beaks strongly excavated; anterior margin very strongly convex; anterior extremity sharply rounded; posterior dorsal margin nearly straight; a prominent umbonal ridge extends from the beaks to the posterior extremity causing a broad and gently curved depressed area along the posterior dorsal margin which is separated from the main surface of the shell by a distinct line or ridge; base broadly arcuate. Resilifer deep and broad; anterior and posterior laterals of left valve high and separated by a groove from the dorsal margin; anterior lateral possibly somewhat shorter and higher than the posterior; cardinal high and prominent. Dimensions: length, 137 mm.; height, 115 mm.; convexity of left valve, 42 mm."
Holotype.--UCMP 11423.
Type locality.--UC 3203. On north slope of Devil's Kitchen, NW 1/4 sec. 32, T. 10 N., R. 21 W., Mt. Pinos Quadrangle, Kern County, Calif. Pleito Formation, Oligocene.
Supplementary description.--"The laterals and the size of the teeth are more like those of the genus Mulinia, but the broad resilifer is like that of the genus Spisula. The form is therefore intermediate." (Wagner and Schilling, 1923, p. 257)
Comparison.--"This form [muliniaformis] is related to S. acutirostrata Packard which was collected by R. E. Dickerson from the Tejon of the Mt. Pinos quadrangle and which was possibly the ancestral form. S. muliniaformis is separable from S. acutirostrata by the larger size, more trigonal outline, and heavier and Mulinia-like teeth." (Wagner and Schilling, 1923, p. 257)
Occurrence in California.--Oligocene: Pleito Formation (Wagner and Schilling, 1923).
Mactromeris abbotti (Wiedey)
Plate 7, figures 1, 3; Plate 7; Plate 7 caption
Spisula abbotti Wiedey, 1928, p. 151-152, pl. 19, figs. 4, 5. Schenck and Keen, 1940, pl. 40, figs. 3, 4.
"Spisula" abbotti Wiedey. Adegoke, 1969, p. 121.
Original description.--"Shell moderate in size, subtriangular in outline, equivalve, inequilateral, thick-set, well inflated, and possesses a heavy shell. The anterior dorsal margin is long, gently concave, and slopes sharply away from the beaks to the anterior dorsal extremity, which is quite abruptly rounded. Basal margin regularly slightly rounded; posterior dorsal margin moderately long and sloping quickly away from the beaks, being slightly concave in contour. The posterior dorsal extremity is less sharply rounded than is the corresponding anterior portion. Umbones very large, prominent, inflated, incurved, exhibiting no distinct umbonal ridge. Beaks moderately large, situated in the anterior portion of the shell, elevated, and slightly prosogyrous. The posterior portion of the shell is the more inflated and the point of greatest thickness falls well up on the valves, just posterior to the beaks. In the attached valves the posterior dorsal areas form together a flattened area which is broad and bounded by sharply rounded, though not angular, shoulders in that portion of the shell. Length, 58 mm.; breadth, 42 mm.; thickness of the attached valve, 31 mm."
Holotype.--SDNM 39.
Type locality.--SU 440. "Two miles [3.2 km] northwest of the power house at the mouth of Kern Canyon [Caliente Quad.], Kern County, California." Temblor Formation, Oligocene and Miocene.
Comparison.--"This species of Spisula [abbotti] is resembled by the common fossil species, S. albaria Conrad, but has a much sharper anterior dorsal extremity, longer, more gently sloping anterior dorsal margin, with sharper umbones than the latter form. Among the living forms it is most closely approximated by S. planulata Conrad, but it is thicker, higher, more equilateral and with a sharper anterior dorsal extremity than the living species." (Wiedey, 1928, p. 152)
Occurrence in California.--Oligocene and Miocene: Temblor Formation (Wiedey, 1928); Miocene: Olcese Sand (Keen and Bentson, 1944).
Mactromeris occidentalis (Gabb)
Plate 7, figures 2, 4; Plate 7; Plate 7 caption
?Hemimactra occidentalis Gabb, 1869, p. 54, pl. 15, figs. 13, 13a.
Spisula occidentalis (Gabb). Packard, 1916, p. 288-289, pl. 23, figs. 1-3. Clark, 1918, p. 157, pl. 11, fig. 1
Spisula (Mactromeris) occidentalis (Gabb). Stewart, 1930, p. 209, pl. 15, fig. 5.
Original description.--"Shell thin, subovate, inequilateral; beaks small, closely approximating, placed about two-fifths of the length from the anterior end, which is broadly excavated above, and prominently, though narrowly rounded below; posterior end convexly and obliquely sub-truncated; cardinal margin sloping and nearly straight, base broadly and regularly convex; a moderately distinct angle runs from the beaks to the posterior basal margin. Surface covered by small but moderately prominent and pretty regularly placed lines of growth."
Holotype.--ANSP 4545.
Type locality.--South of Martinez [Contra Costa County], Calif. San Ramon Formation, Miocene(?).
Supplementary description.--"The hinge plate is wide; chondrophore deep and slightly roofed; left cardinal is somewhat broken, but the remaining portion shows that the arms were of nearly equal length and that the tooth was situated medially upon the hinge plate; arms of the right cardinal heavy, the anterior one not confluent with, nor in the same plane with the ventral lamina; laterals but imperfectly preserved, the anterior one arising from the ventral edge of the hinge plate, and distant from and not in alignment with the anterior cardinal arm; laminae short and low, the posterior ventral one being the largest; ventral sinus is restricted by an abrupt inbending of the ventral margin of the hinge plate. Pallial sinus extends to the middle of the shell." (Packard, 1916, p. 288)
"There is almost a definite concentric sculpture on the umbonal region but it is completely obscured by the prominent growth lines in the later portion of shell. The lunule is slightly depressed but not circumscribed. There are two faint posterior umbonal ridges. Length [holotype] 71 mm.; height, 57.8 mm.; thickness of both valves, 30.2 mm." (Stewart, 1930, p. 209)
Comparison.--"Although the ratio of the height to the length of this species [occidentalis] is quite variable, this form is quite readily separable from other known mactrine species. Certain specimens might possibly be confused with a young specimen of S. catilliformis, but the lack of the characteristic posterior flexure of that species and the widely different type of dentition easily characterizes Gabb's species [occidentalis]." (Packard, 1916, p. 289)
Occurrence in California.--Eocene and Oligocene: San Lorenzo Formation (Clark, 1918); Oligocene: Kirker Tuff (Clark in Lawson, 1914); Miocene(?): San Ramon Formation (Clark, 1918; Weaver, 1949).
Mactromeris catilliformis catilliformis (Conrad)
Plate 8, figures 1-3, 9; Plate 8; Plate 8 caption
Spissula [sic. Spisula] catilliformis Conrad, 1867, p. 193.
Spisula catilliformis Conrad. Dall, 1894, p. 137, pl. 5, fig. 3. Arnold, 1903, p. 176, pl. 19, fig. 5. Not Clark, 1915, pl. 59, fig. 1. Not Packard, 1916, p. 285-286, pls. 17, 18, 19. Packard, 1918, p. 282, pl. 27, figs. 1, 2. Oldroyd, 1924, p. 194, pl. 24, fig. 1. Loel and Corey, 1932, p. 232, pl. 44, fig. 8.
Mactra (Spisula) catilliformis (Conrad). Grant and Gale, 1931, p. 398, pl. 23, figs. 4, 10.
"Spisula" catilliformis Conrad. Adegoke, 1969, p. 121.
Macatromeris catilliformis (Conrad, 1867. Coan, Scott, and Bernard, 2000, p. 454, pl. 95.
Original description.--"Suboval, inequilateral; anterior side slightly flattened or contracted; posterior side with an oblique shallow groove or fold; lines of growth coarse and prominent; lunule very long, elliptical; ventral margin tumid posteriorly; cardinal pit oblique, large; pallial sinus extending beyond the middle of the valve."
Holotype.--Location unknown.
Type locality.--Panama, Holocene (Packard, 1916, p. 286); described in error from Panama (E.V. Coan, P.H. Scott, and F.R. Bernard, written commun.,1994)
Supplementary description.--"The hinge plate of this species is wide; chondophore very large and shallow, overhung slightly by the arm of the cardinal and by a prominent spur; left cardinal heavy, large, situated on the dorsal edge of the hinge plate; arms of nearly equal length; ventral sinus wide, flat; right cardinal low, anterior arm small, appressed to the dorsal margin of the shell; posterior arm thin, overhanging the chondophore; laterals heavy, anterior lateral short, high and fused to the dorsal side of the anterior cardinal arm; posterior lateral longer and not quite so high as the anterior one; laminae very short, heavy, and close to the umbones; anterior dorsal lamina nearly in the same plane with the anterior cardinal arm. Pallial sinus deep, rounded, reaching nearly to the middle of the shell." (Packard, 1916, p. 285)
Occurrence in the Californias.--Miocene: Briones Formation, (Trask, 1922) and Cierbo and Neroly Sandstones(Weaver, 1949; Hall, 1960) San Pablo Group, Monterey Group (Weaver, 1949), and Sobrante Sandsone (Lutz, 1951); Miocene and Pliocene: Etchegoin (Adegoke, 1969) and Tahana Member of the Purisima (Addicott, 1968) Formations: Pliocene: Careaga (Keen and Bentson,1944), San Diego (Arnold, 1906) and San Joaquin (Adegoke, 1969) Formations; Pliocene and Pleistocene: Fernando Formation (Soper and Grant, 1932) and Wildcat Group (Faustman, 1964); Pleistocene: San Pedro Formation (Arnold, 1907a) and unnamed strata at Potrero Canyon (Valentine, 1956), Torrey Pines State Park (Valentine, 1960), and in Baja California Norte (Valentine and Rowland, 1969).
Habitat.--In 5 to 20 m, in sand and sandy mud of bays and exposed shorelines. (Coan, Scott, and Bernard, 2000, p. 254) Living Washington to southern California.
Mactromeris catilliformis lenticularis (Gabb)
Plate 8, figure 4; Plate 8; Plate 8 caption
Hemimactra lenticularis Gabb, 1866, p. 19, pl. 4, fig. 33.
Spisula lenticularis (Gabb). Packard, 1916, p. 302.
Spisula (Mactromeris) catilliformis lenticularis (Gabb). Stewart, 1930, p. 208-209, pl. 16, fig. 4.
Original description.--"Shell large, flattened, thin, inequilateral, irregularly subquadrate; beaks eccentric, large, slightly curved forwards and inwards; anterior end broadly concave below the beaks and convex below; base and posterior end regularly convex; cardinal margin sloping nearly straight. Hinge teeth slender. Pallial sinus moderately deep, round at the base. Surface marked by irregular lines of growth."
Lectotype.--ANSP 4549. (Stewart, 1930, p. 208-209)
Type locality.--Near Martinez [Contra Costa County], California. San Ramon Formation, Miocene(?).
Supplementary description.--"The lunule and escutcheon are marked by large, slightly depressed areas, but are not otherwise defined. The posterior umbonal ridge is very faint but evident. It has been possible to expose part of the hinge of the lectotype, a right valve, revealing the two deep lateral sockets with their parallel ridges. Length [holotype] (incomplete), 77 mm.; Height (incomplete), 61 mm.; width, of right valve, ca. 14 mm." (Stewart, 1930, p. 209)
Comparison.--"The anteriorly placed beaks of this form [lenticularis] are suggestive of the Recent S. catilliformis Conrad but the fossil is not so inflated as the few Recent specimens available in the National Museum. However, according to Packard (1916) S. catilliformis is variable and it may be that specimens are known that connect these two forms, therefore the fossil is treated as a subspecies." (Stewart, 1930, p. 209)
Occurrence in California.--Miocene(?): San Ramon Formation (Keen and Bentson, 1944).
Mactromeris catilliformis alcatrazensis (Arnold)
Spisula catilliformis Conrad var. alcatrazensis Arnold, 1907a, p. 437, pl. 56, fig. 6. Arnold and Anderson, 1907, p. 148, pl. 23, fig. 6.
Original description.--"Shell averaging about 130 millimeters in longitude, oval in outline, slightly narrower in front than behind, equivalve, inequilateral, ventricose, extremities slightly gaping; base regularly arcuate, posterior portion of dorsal margin nearly straight at umbo, gradually becoming more and more arcuate as it passes around the broadly rounded extremity; anterior dorsal margin only slightly depressed in front of umbo, but carrying a slight bump only a short distance from the latter; anterior extremity more truncate and narrower than posterior; beaks slightly anterior, bent forward, but not exceptionally prominent. Surface consists of numrous more or less irregular lines of growth. Hinge and interior quite similar to typical form."
Holotype.--USNM 165291.
Type locality.--USGS 4471. Alcatraz asphalt mine, near Sisquoc, Santa Barbara County, Calif. Careaga Sandstone, Pliocene.
Supplementary description.--"Longitude, 128 mm.; altitude, 98 mm.; diameter, 57 mm." (Arnold, 1907a, p. 437)
Comparison..--"This variety [alcatrazensis] is more ventricose, more excavated and attenuate in front, more regularly rounded below, and has the beaks more central than the typical S. catilliformis." (Arnold, 1907a, p. 437)
Occurrence in California.--Pliocene: Careaga Formation (Keen and Bentson, 1944).
Mactromeris albaria albaria (Conrad)
Plate 9, figures 1, 2, 7, 9; Plate 9; Plate 9 caption
Mactra albaria Conrad, 1848, p. 432, fig. 4.
Spisula albaria (Conrad). Clark, 1925, p. 99. Packard, 1916, p. 290-291, pl. 24, fig. 1; pl. 25, figs. 3-8.
Spisula (Mactromeris) albaria (Conrad). Etherington, 1931, p. 86, pl. 10, figs. 8, 9. Moore, 1963, p. 82-83, pl. 28, figs. 1-3, 5; pl. 31, figs. 9, 11. Roth, 1979, p.312-314.
Original description.--"Triangular, ventricose; beaks medial; umbonal slope angulated; anterior and posterior margins nearly equally oblique; posterior extremity truncated, direct; basal margin regularly curved."
Holotype.--Missing and presumed lost.
Type locality.--Astoria, Oregon. Astoria Formation, Miocene.
Supplementary description.--"Spisula albaria is of small to moderate size and varies in outline between forms subovate and almost equilateral***to ones that have the anterior end markedly produced***. There is no variation in the hinge of the forms studied, and in addition the same amount of variation in outline has been noted in single collections of Recent species of Spisula. Well-preserved specimens of S. albaria show a prominent posterior ridge extending from the umbo to the ventral margin and bordered on either side by a slight depression***. The concentric lines are more prominent on this ridge than elsewhere on the shell. One specimen was collected***that shows a broad anterior furrow extending from the umbo along the anterior margin to the ventral edge of the shell***.
"The right anterior cardinal tooth is thin and blade-like and almost parallels the dorsal margin of the shell, to which it is fused***. The middle cardinal borders the anterior edge of the chondrophore, which is fairly deep and oblique and seems to have been partly roofed over at the dorsal margin. Both the anterior and the posterior laterals are thin and bladelike, parallel and close to the dorsal margin and bordered dorsally by a moderately deep pit and ventrally by a very deep pit. The left anterior cardinal***is bifid and projects beyond the hinge plate. There apparently was a thin bladelike posterior cardinal paralleling the anterior cardinal and barely separated from it. The anterior and posterior laterals are thin and border the ventral margin of the hinge plate, being separated from the dorsal margin by a moderately deep groove. (Moore 1963, p. 83)
Comparison.--"Spisula albaria is closely related to S. albaria var. ramonensis, from which it differs in being typically more elongate, with a narrower hinge plate and shorter laterals, which are more intimately connected with the cardinal arm. It differs from S. selbyensis in being more nearly equilateral, in its wider hinge plate, less compressed left cardinal, shorter laminae and in the less intimate connection between the anterior ventral lamina and the cardinal arm." (Moore, 1963, p. 83)
Occurrence in California.--Oligocene and Miocene: Temblor Formation (Moore, 1963); Miocene: Cierbo and Neroly Sandstones, San Pablo Group (Weaver, 1949; Hall, 1960), Monterey Group (Weaver, 1949), Santa Margarita Formation (Weaver, 1949; Adegoke, 1969), and Sobrante Sandstone (Lutz, 1951); Miocene and Pliocene: Etchegoin Formation (Moore, 1963), Tahana Member of the Purisima Formation (Addicott,1969); Pliocene: Ohlson Ranch Formation (Peck, 1960); Pliocene and Pleistocene: Merced Formation (Weaver, 1949).
Mactromeris albaria selbyensis (Packard)
Plate 9, figures 4, 8; Plate 9; Plate 9 caption
Spisula selbyensis Packard, 1916, p. 292-293, pl. 26, figs. 2a, 2b, 3.
Spisula albaria (Conrad) var. selbyensis Packard. Lutz, 1951, p. 388, pl. 15, figs. 1, 3.
Original description.--"Shell inequilateral, somewhat ventricose; umbones rather prominent, adjacent, generally situated posterior to the middle of the shell; area below and anterior to the beaks strongly excavated; anterior dorsal edge nearly straight, sloping regularly to the broadly rounded anterior extremity; posterior dorsal edge broadly rounded, meeting a slight truncation at the base; base arcuate; surface marked by a varying number of incremental lines of growth; hinge plate very narrow; chondophore deep and somewhat compressed; left cardinal high, arms of nearly equal length, not widely diverging; this tooth extends from the dorsal to the ventral margin of the hinge plate; ventral sinus very restricted; laterals long, low, round-topped, arising from the ventral margin of the plate; base of the anterior lateral not reaching to the cardinal arm; right cardinal well developed, with a heavy anterior arm, which is closely appressed to the margin of the shell; posterior arm also heavy, reaching to the ventral border of the plate; anterior ventral lamina long, in the same plane with, and joining the anterior cardinal arm by a low ridge. The dimensions of the type are: length, 29 mm., convexity, 10 mm."
Holotype.--UCMP 11483.
Type locality.--UC 1352. "One-third of a mile [0.5 km] south-west of Vallejo Junction, in a bluff close to the railroad track at the lowest Miocene contact with the Martinez, Napa sheet [Napa County, California]." Monterey Group, Miocene.
Supplementary description.--"The shape of this species is exceedingly variable. The beaks are in some specimens anterior to the middle of the shell, while in others from the same collecting locality they are posterior to that line." (Packard, 1916, p. 293)
Comparison.--"This species [selbyensis] resembles S. albaria in general outline, but it differs from that species in that it is generally more inequilateral and more elongate, with a narrower hinge plate, and more compressed left cardinal. The length of the laminae and the close relationships between the anterior ventral lamina and the cardinal arm also characterize this species." (Packard, 1916, p. 293)
Occurrence in California.--Miocene: Monterey Group (Packard, 1916) and Sobrante Sandstone (Lutz, 1951).
Mactromeris albaria coosensis (Howe)
Plate 9, figures 3, 6; Plate 9; Plate 9 caption
Spisula (Hemimactra) albaria (Conrad). Dall, 1909, p. 130-131, pl. 10, fig. 1. Packard, 1916, p. 290. Not Mactra albaria Conrad, 1848, p. 432, fig. 4.
Spisula albaria Con. var. coosensis Howe, 1922, p. 99-100, pl. 9, figs. 6, 7. New name for Spisula albaria of Dall, 1909, and of Packard, 1916.
Spisula (Mactromeris) albaria (Conrad) var. coosensis Howe. Weaver, 1943, p. 242, pl. 56, fig. 3; pl. 57, figs. 2, 11.
Spisula albaria coosensis Howe. Addicott, 1969, p. 71, pl. 3, figs. 1, 6, 8; pl. 4, figs. 8, 9.
Spisula albaria oregonensis Clark, 1925, p. 100-101, pl. 17, figs. 5-7.
Spisula (Mactromeris) albaria (Conrad) subsp. oregonensis Clark. Weaver, 1943, p. 241, pl. 56, figs. 1, 5, 8.
Original description.--"Shell subequilateral, beaks a little anterior to median line, strongly inturned but only slightly prosogyrous. Posterior end broadly rounded with faint suggestion of being truncated, the result of a somewhat obscure umbonal ridge between beaks and posterior end; anterior end broadly and regularly rounded; posterior dorsal edge long and gently convex; anterior dorsal edge straight, dorsal margin rather strongly depressed; suface smooth except for rather coarse irregular incremental lines. Hinge plate fairly heavy; anterior cardinal of right valve fused with dorsal margin and does not extend to anterior edge of the chondrophore; claspers fairly heavy and well-developed; outer claspers fused to dorsal margins. Deltoid cardinal heavy, covering almost entire width of hinge plate. Laterals prominent, tops round, posterior or lateral longer than anterior with abrupt ventral slope. Dimensions of type specimen: Length 67 mm.; height 54 mm.; diameter, one valve, 15 mm."
Holotype.--UCMP 30028.
Type locality.--UC 3325. Coos Bay, Oregon. Empire Formation, Pliocene.
Comparison.--"These specimens (albaria) from Astoria and Newport all show the left cardinal to extend uniformly from the beaks to the edge of the chondrophore, while in var. coosensis the left cardinal extends only two-thirds of this distance.
"In the right valve of Spisula albaria, the posterior portion of the cardinal parallels the dorsal margin and is fused to it, while in var. coosensis, though partially fused to the dorsal margin, it does not parallel it by any means, but makes a ten degree angle." (Howe, 1922, p. 100)
"Spisula coosensis has shorter superior laminae in the right valve and attains a larger size than S. albaria (Conrad) from the Astoria Formation." (Roth, 1979, p. 316)
Comments.--Dall, 1909, p. 130 described a specimen as Spisula albaria that had been collected by Camman from the Empire Formation, Oregon, and Packard (1916, p. 290) based his description of albaria on a specimen from the Merced Formation, California (Howe, 1922, p. 99-100). Howe (1922, p. 99-100) proposed the new name Spisula albaria Con. var. coosensis for these specimens.
Occurrence in California.--Miocene and Pliocene: Purisima Formation (Roth, 1972; Perry, 1988); Pliocene and Pleistocene: Merced Formation (Weaver, 1949; Yancey, 1978; Roth, 1979).
Mactromeris mossbeachensis (Glen)
Plate 10, figures 3, 5; Plate 10; Plate 10 caption
Spisula (Hemimactra) mossbeachensis Glen, 1959, p. 175, pl. 15h; pl. 16a.
Original description.--"Shell of medium size, very elongate, thin, compressed, height less than two-thirds length; beaks considerably posterior to middle of shell; lunule well developed, extending to extreme anterior margin; both anterior and posterior dorsal edges convex with posterior edge more steeply sloping; umbones small, sharply pointed; umbonal angle 145° to 160°; posterior margin gently rounded, anterior margin sharply curved at termination of lunule; fairly prominent posterior gape; hinge plate narrow; chondophore small and shallow, open at ventral end; right cardinal high with anterior arm strongly developed and close to dorsal margin of shell; left cardinal thin, high, anterior arm longer than posterior; anterior laterals of right valve very short, posterior laterals slightly longer; ligament and resilium not separated by shelly partition."
Holotype.--UCMP 37643.
Type locality.--UC B-4790. "On Moss Beach, 240 feet [75 m] N. 40°W. of the mouth of the first small, unnamed, intermittent creek north of San Vicente Creek, in an almost horizontal, soft, friable, gray, fine-grained, massive, fossiliferous, sandstone bed, approximately 5 feet [1.5 m] thick; in the center of the nose of the Moss Beach syncline, accessible only at low tide."
Comparison.--"This species may be differentiated from other species of the genus by its extreme length and large umbonal angle." (Glen, 1959, p. 175).
Occurrence in California.--Miocene and Pliocene: Tahana Member, Purisima Formation (Addicott, 1969); Pliocene and Pleistocene: Merced Formation (Yancey, 1978).
Mactromeris sisquocensis (Arnold)
Spisula sisquocensis Arnold, 1907, p. 19-20, pl. 56, fig. 1. Arnold and Anderson, 1907, p. 148, pl. 23, fig. 1. Packard, 1916, p. 302-303. Grant and Gale, 1931, p. 399.
Original description.--"Shell averaging about 120 millimeters in longitude, subtrigonal in outline, equivalve, inequilateral, ventricose; base regularly arcuate; beaks anterior, prominent, bent forward, protruding beyond periphery or [of] shell; anterior end shorter and narrower than posterior, which is evenly rounded; area in front of beaks depressed concavely as a whole, but slightly elevated at margin, this condition, when the two valves are together, suggesting a large lunule with a slightly raised ridge running down the middle; posterior margin becomes more and more arcuate as extremity is approached, sculpture consisting of numerous fine incremental lines, some of which are more prominent than the great majority, these more prominent ones giving a slightly irregular surface to the shell. Hinge and interior unknown, but probably quite similar to S. hemphilli."
Holotype.--USNM 165292.
Type locality.--USGS 4471. Alcatraz asphalt mine, near Sisquoc, Santa Barbara County, Calif. Careaga Sandstone, Pliocene.
Supplementary description.--"Longitude, 120 mm.; altitude, 85 mm.; diameter, 59 mm." (Arnold, 1907, p. 20)
Comparison.--"This species [sisquocensis] is near S. hemphilli Dall, but is constantly and decidedly narrower. (Arnold, 1907, p. 20).
Occurrence in California.--Pliocene: Careaga Sandstone (Keen and Bentson, 1944).
Mactromeris voyi (Gabb)
Callista voyi Gabb, 1866, p. 24. Gabb, 1869, p. 96, pl. 5, fig. 41.
Spisula voyi (Gabb). Packard, 1916, p. 283-285, pl. 15, figs. 1a, 1b, 2. Oldroyd, 1924, p. 193, pl. 23, figs. 1, 2.
Spisula polynyma (Stimpson) voyi (Gabb). Stewart, 1930, p. 207-208, pl. 15, fig. 6.
Original description.--"Shell broad, inequilateral; beaks in advance of the middle; cardinal margin nearly straight and sloping; anterior end very much produced, rounded and narrow; posterior end obliquely truncated; base broadly and regularly rounded. Surface marked by numerous irregular and rather strong lines of growth."
Holotype.--MCZ 15038.
Type locality.--Humboldt Bay, below Bear River, Humboldt County, Calif. Wildcat Group, Pliocene and Pleistocene.
Supplementary description.--"The hinge plate of this species is wide, the chondophore oblique, shallow, very slightly overhung by the posterior arm of the cardinal; left cardinal heavy, high, situated on the dorsal portion of the hinge plate; arms heavy, of equal length, free from accessories, ventral sinus excavated; right cardinal low, anterior arm thick, appressed to the shell margin; posterior arm very thin; anterior lateral low, acutely pointed, its dorsal base extending back of, and parallel to the anterior arm of the cardinal; posterior lateral low, long, reaching as an indistinct ridge nearly to the umbones; posterior laminae low and long; anterior laminae very short; dorsal one arises from the margin of the shell. Pallial sinus of the Recent specimens deep, rounded and oblique to the pallial line." (Packard, 1916, p. 284)
Comparison.--"The hinge of this species [voyi] might be confused with that of S. catilliformis. It differs from that species in that the anterior arm of the cardinal and that of the posterior laminae are much more elongate." (Packard, 1916, p. 284)
"This subspecies [voyi] is more elongate than typical Spisula polynyma Stimps." (Stewart, 1930, p. 208)
Occurrence in California.--Pliocene and Pleistocene: Merced Formation (Packard, 1916; Weaver, 1949), Rio Dell Formation (Faustman, 1964), and Wildcat Group (Packard, 1916).
Mactromeris brevirostrata (Packard)
Plate 10, figures 1, 7; Plate 10; Plate 10 caption
Spisula brevirostrata Packard, 1916, p. 296-297, pl. 28, figs. 1a, 1b, 2. Grant and Gale, 1931, p. 395.
Spisula (Mactromeris) brevirostrata Packard. Roth, 1979, p. 314-315, pl. 6, fig. 1.
Original description.--"Shell medium-sized, compressed, equilateral, umbones small, adjacent; anterior dorsal edge sloping in a nearly straight line to the rather attenuated anterior extremity. A fairly distinct ridge, extending from the umbones to the anterior extremity, limits a depressed area on the anterior margin of the shell; posterior dorsal edge very slightly convex, sloping regularly to the broadly rounded extremity; base arcuate. Hinge plate relatively wide; chondophore very shallow, triangular in shape, probably overhung by a small spur; left cardinal large, not overhanging the resilifer, situated ventrally on the hinge plate; arms of equal length, their ventral edges rounded; laterals high, short; anterior one round-topped and shorter than the posterior one, which is acutely pointed; dorsal base of the anterior lateral is close to, but slightly dorsal to, the anterior arm of the cardinal. Pallial line distant, pallial sinus reaching nearly to the middle of the shell. Hinge of the right valve unknown. The dimensions of the type are: length, 78 mm., height, 60 mm., convexity, 15 mm."
Holotype.--UCMP 11489.
Type locality.--UC 1875. "Along the east bank of Eel River one mile [1.6 km] north of Scotia, Humboldt County, California." Wildcat Group, Pliocene and Pleistocene.
Comparison.--"This species [brevirostrata] has been confused with S. falcata, from which it differs in being relatively higher and in possessing a large left cardinal the arms of which are of equal length." (Packard, 1916, p. 296)
"This extinct species [brevirostrata] is distinguished from S. polynyma, with which it occurs in the upper part of the Wildcat Group, by its more central beaks, sharper umbonal angle, blunt radial keels anteriorly and posteriorly, and broad, inturning, posterior dorsal slope which pouts slightly just behind the beaks." (Roth 1979, p. 314).
Occurence in California.--Pliocene and Pleistocene: "Merced" (Roth, 1979) and Rio Dell (Faustman, 1964) Formations and Wildcat Group (Packard, 1916).
Mactromeris mercedensis (Packard)
Plate 11, figures 1-3, 5, 7; Plate 11; Plate 11 caption
Spisula mercedensis Packard, 1916, p. 286-287, pl. 20 [not pl. 13 as stated, according to Keen and Bentson 1944, p. 110].
Original description.--"Shell large, ventricose, inequilateral, the beaks being considerably anterior to the middle of the shell; anterior dorsal edge short, slightly concave, with a faint suggestion of a lunule; posterior dorsal edge gently convex, curving regularly to the rounded extremity; anterior end evenly rounded; base broadly arcuate; umbones small, sharply pointed; an indistinct posterior flexure extends from the umbones to the base, much as in Spisula catilliformis Conrad. Surface roughened by numerous irregular lines of growth. Hinge plate wide, chondophore shallow, wide, overhung but slightly by the posterior arm of the cardinal; left cardinal large, arms of equal length, high; anterior lateral short, situated dorsal to the anterior arm of the cardinal; posterior lateral high and acutely pointed. Hinge of the right valve unknown. Pallial sinus not observed. The dimensions of the type are: length 124 mm., height 93 mm., convexity 32 mm."
Holotype.--UCMP 11467.
Type locality.--"***marine cliffs***near Mussel Rock, San Mateo County, California." Merced Formation, Pliocene and Pleistocene.
Comparison.--"This species differs from Spisula catilliformis, with which it is often associated, in its general outline; in being more ventricose; in having an indistinct posterior flexure and in the separation of anterior lateral from the anterior arm of the cardinal." (Packard, 1916, p. 287)
Occurrence in California.--Miocene: Pancho Rico Formation (Durham and Addicott, 1965); Pliocene and Pleistocene: Merced Formation (Packard, 1916; Yancey, 1978).
Mactromeris hemphillii (Dall)
Plate 11, figures 4, 6; Plate 11; Plate 11 caption
Mactra hemphillii Dall, 1894, p. 137, pl. 5, fig. 2.
Spisula hemphillii (Dall). Arnold, 1903, p. 175, pl. 19, fig. 3. Packard, 1916, p. 287-288, pls. 21, 22. Oldroyd, 1924, p. 194, pls. 46, 50.
"Spisula" hemphilli (Dall). Adegoke, 1969, p. 122.
Mactromeris hemphillii (Dall, 1894). Coan, Scott, and Bernard, 2000, p. 454, pl. 95.
Original description.--"Shell large, thin, inflated, subequilateral, creamy white with a yellow thin epidermis, which over the body of the shell in young shells is beautifully evenly concentrically striated and on the posterior dorsal area is irregualrly wrinkled, with an elevated raphe of epidermis at the margin of the area; beaks rather prominent, the anterior end of the valves longer than the posterior; posterior dorsal slope excavated; lunule obscure, escutcheon marked by prominent elevated radial lines of epidermis; the dorsal margin pouting in front of the ligament, the posterior slope convex, the posterior flexure faint, but marked by a recession of the ventral border of the valves, which gap but very little and not at all in front; anterior end rounded, but smaller than the posterior; ventral border arcuate; hinge and pallial sinus much as in the last species [S. catilliformis] except that the sinus is smaller and less depressed."
Holotype.--USNM 15815.
Type locality.--San Diego, Calif. Holocene.
Supplementary description.--"Hinge plate rather wide, chondophore deep, apically roofed by a prominent spur, but not overhung by the cardinal arms; left cardinal high and heavy, situated on the dorsal portion of the hinge plate; arms of equal length; ventral sinus deeply excavated; right cardinal low, the cardinal arms not fused medially, anterior arm the heavier, posterior arm short and thin; anterior lateral short, high, round-topped, distinctly separate from and in nearly the same plane with the anterior cardinal arm; laminae short and heavy; anterior ventral lamina distant from, but nearly in alignment with the anterior cardinal arm; dorsal anterior lamina represented by a short, low process arising from the margin of the shell; posterior dorsal lamina shorter and thinner than the posterior ventral one. Pallial sinus deep, oblique to the ventral margin. The dimensions of the type***were given as: length 120 mm., height 93 mm., convexity 25 mm." (Packard, 1916, p. 288)
Comparison.--"This species [hemphilli] might be confused with S. catilliformis. From that species it is separable on the basis of its shape; longer laminae; the separation of the anterior lateral from the arm of the cardinal; and the more oblique type of pallial sinus." (Packard, 1916, p. 288)
Occurrence in California.--Miocene and Pliocene: Etchegoin (Adegoke, 1969), Merced (Martin, 1916), Purisima (Arnold, 1906), and Towsley (Kern, 1973) Formations; Pliocene and Pleistocene: Fernando (Soper and Grant, 1932) and Merced (Martin, 1916) Formations; Pleistocene: San Pedro Formation (Arnold, 1903) and unnamed strata in Potrero Canyon (Valentine, 1956), Newport Bay (Kanakoff and Emerson, 1959), and in Baja California Norte (Valentine, 1957).
Habitat.--In the intertidal zone to 50 m, in sand and mud of protected areas. (Coan, Scott, and Bernard, 2000, p. 454) Living southern California to Baja California Sur.
"Mactromeris weaveri Packard"
Plate 8, figure 5; Plate 8; Plate 8 caption
Spisula (?) weaveri Packard in Dickerson, 1914, p. 139-140, pl. 12, figs. 4a, 4b. Packard, 1916, p. 313, pl. 27, fig. 9.
Original description.--"Shell small, relatively thick, subtrigonal to oval, moderately ventricose, evenly rounded; umbones nearly central, prosogyrate, prominent, nearly adjacent; anterior dorsal margin concave for a distance equal to about one-third the height of the shell; anterior extremity slightly attenuated, evenly rounded; base broadly rounded, curving gently in the dorsal region to the beak; surface roughened by coarse lines of growth; hinge and interior but imperfectly known. The dimensions of the type are: length 32 mm., height, 26 mm., convexity, 5 mm."
Syntypes.--UCMP 11713, 11714.
Type locality.--UC 1556. Contra Costa County, Calif. Martinez Formation, Paleocene.
Comments.--Smith (1975) says that Spisula (?) weaveri is not a mactrid and should be assigned to "Arctica".
Occurrence in California.--Paleocene: Martinez Formation (Dickerson, 1914; Packard, 1916).
Genus MACTROMERIS?
Mactromeris? aequilateralis (Waring)
Plate 8, figure 6; Plate 8; Plate 8 caption
Spisula aequilateralis Waring, 1917, p. 80, pl. 14, fig. 8.
Original description.--"Shell small, convex, equilateral, trigonal; beaks adjacent, sharp, with sides sloping equally either way; ligament sagitate; basal margin broadly curved; surface marked by fine lines of growth, umbonal ridges sharp."
Holotype.--CAS/SU 154; CAS 61927.01, new number.
Type locality.--Simi Hills, Camulos Quad., Ventura County, Calif. Martinez Formation, Paleocene.
Occurrence in California.--Paleocene: Martinez Formation (Waring, 1917).
Mactromeris? tenuissima (Gabb)
?Mactra tenuissima Gabb, 1869, p. 179, pl. 29, fig. 68.
Mactra? tenuissima Gabb. Dickerson, 1914, p. 151, pl. 12, fig. 5. Packard, 1916, p. 312.
Cymbophora tenuissima (Gabb). Stewart, 1930, p. 213, pl. 1, fig. 3.
Original description.--"Shell small, extremely thin, subequilateral; beaks central, small, pointed slightly in advance; anterior end obliquely and convexly subtruncated; base regularly convex. Surface marked by minute, concentric striae of growth; an angulated ridge runs from the umbones to the posterior basal angle. Palial sinus deep and narrow."
Holotype.--ANSP 4361.
Type locality.--Martinez [Contra Costa County], Calif. Martinez Formation(?), Paleocene(?).
Supplementary descirption.--"Lunule and escutcheon are not defined. There is a faint posterior umbonal ridge.***Length, incomplete, 27.3 mm.; height, 20.5 mm.; thickness of left valve, ca. 5 mm." (Stewart, 1930, p. 213)
Occurrence in California.--Cretaceous(?): unknown formation or Paleocene(?): Martinez Formation(?) (Dickerson, 1914).
Mactromeris? merriami (Packard)
Plate 11, figures , 2, 5, 7; Plate 11; Plate 11 caption
Spisula merriami Packard, 1916, p. 294-295, pl. 27, figs. 3a, 4. Vokes, 1939, p. 97, pl. 15, figs. 12-13. Weaver, 1943, p. 233-234, pl. 52, figs. 11-12. Stewart, 1946, pl. 11, fig. 23. Squires, 1987, p. 67, fig. 114. Not Dickerson, 1916, p. 485-486, pl. 39, figs. 2a-c.
Original description.--"Shell small, trigonal, equivalve nearly equilateral, ventricose, ornamented by numerous fine concentric ridges, which are more pronounced and less numerous on the anterior and posterior dorsal areas than upon the other portions of the shell; beaks moderately prominent, anterior dorsal area limited by a distinct ridge extending from the umbo to the anterior extremity; the margin of this area is nearly straight; posterior dorsal slope slightly convex, limited by an indistinct ridge which extends from the beak to the base of the shell; anterior extremity more sharply pointed than the posterior; base very broadly rounded. Hinge plate relatively broad, chondophore oblique, shallow, apically roofed by a broad flat spur; left cardinal prominent, high, arms broad, extending from the dorsal to the ventral margin of the plate; ventral sinus narrow, flat; right cardinal with a prominent anterior arm and a well-developed, although relatively thin posterior arm; laminae long, distant from the beaks; anterior lateral formed from the margin of the plate, top rounding, distant from the anterior arm of the cardinal; posterior lateral also with a rounding top, dorsal and ventral slopes nearly equal; anterior ventral lamina formed from the upturned edge of the hinge plate, not confluent with the anterior cardinal arm; anterior dorsal scarcely developed, considerably smaller than the corresponding posterior one."
Holotype.--UCMP 11484.
Type locality.--UC 672. "Coalinga Quadrangle, Fresno County, California, SE 1/4 of NW 1/4 of Sec. 24, T 18 S, R 14 E, Parson's Peak, in Tejon white sandstones. About ten feet [3 m] below white shale." Domengine Formation, Eocene (Keen and Bentson, 1944).
Supplementary description.--"This species is characterized by a distinct ridge that extends posteriorly from the beak to the ventral margin and another ridge that extends anteriorly from the beak to the ventral surface." (Squires, 1987, p. 67)
Comparison.--"Additional topotype specimens of S. merriami show that not all the individuals develop prominent concentric ribbing over the entire surface of the shell and many exhibit a sculpturing almost exactly similar to that of S. bisculpturata Anderson & Hanna (1925: 149. pl. 3, f. 7). Merriami appears to differ from that species in being more equilateral and in lacking or possessing a less prominent depression behind the anterior umbonal ridge." (Vokes, 1939, p. 97)
Occurrence in California.--Eocene: Avenal Sandstone (Stewart, 1946), Domengine (Vokes, 1939), and Juncal (Squires, 1987) Formations.
Mactromeris? markleyensis (Clark)
Plate 8, figure 8; Plate 8; Plate 8 caption
Mactra (Spisula) markleyensis Clark, 1938, p. 699, pl. 2, figs. 1, 6, 7.
Original description.--"Shell nearly equilateral; beaks central, inconspicuous; anterior and posterior ends subangulate with nearly flat depressed dorsal margins separated from the main surface of the shell by umbonal ridges which are well developed from the beaks to the ventral edge. Surface smooth except for incremental lines which are much more conspicuous on the depressed dorsal margins. Hinge plate of the left valve with a fairly long, bluntly rounded anterior lateral; posterior lateral broken. The resilifer is well defined, separated from the fairly broad ligamental area by a low but distinct ridge; cardinal deltoid-shaped, of moderate size, above which, and hanging out over the resilifer pit, is a distinct spur."
Holotype.--UCMP 30852.
Type locality.--UC A-1297. Solano County, Calif. Markley Formation, Eocene.
Occurrence in California.--Eocene: Markley Formation (Clark, 1938).
Mactromeris? gaviotaensis (Conrad)
Plate 8, figure 7; Plate 8; Plate 8 caption
Mactra(?) gabiotensis Conrad, 1857, p. 194, pl. 7, fig. 3. Packard, 1916, p. 313. Woodring, 1931, p. 380-381.
Spisula gaviotaensis (Conrad). Weaver and Kleinpell, 1963, p. 206, pl. 37, figs. 3, 4.
Original description.--"Triangular, equilateral; anterior extremity acutely rounded, posterior extremity subangulated; umbonal slope carinated, slightly curved."
Holotype.--USNM 13310 (Woodring, 1931, p. 380).
Type locality.--Gaviota Pass [Santa Barbara County], California. Gaviota Formation, Eocene and Oligocene.
Comparison.--"Though it [gaviotaensis] is closely related to Spisula merriami Packard from the Domengine and S. bisculpturata Anderson and Hanna from the type Tejon, it is entirely distinct, but perhaps is a descendant from these earlier forms. It is distinguished from both by greater ventricosity, more strongly developed anterior and posterior umbonal carina, generally larger size, and longer radius for the ventral margin. It is perhaps more closely related to S. bisculpturata in that the depression is behind the posterior umbonal ridge and is best developed on the left valve." (Weaver and Kleinpell, 1963, p. 206)
Comments.--Packard (1916, p. 313) considered gabiotensis to be an invalid species, but Woodring (1931, p. 380) said that "***Conrad's poorly figured and described species can not be so lightly disposed of."
Weaver and Kleinpell (1963, p. 206) considered M.(?) gabiotensis of Conrad to be a lapsus calami for M.(?) gaviotaensis and corrected the spelling. The fact that the holotype was described from Gaviota Pass lends credence to their theory and the correction is herein accepted.
Occurrence in California.--Gaviota Formation (Keen and Bentson, 1944).
Mactromeris? sectoris (Anderson and Martin)
Plate 5, figures 12, 14, 15; Plate 5; Plate 5 caption
Mactra sectoris Anderson and Martin, 1914, p. 63-64, pl. 3, figs. 5a-5e. Loel and Corey, 1932, p. 231, pl. 45, fig. 4. Adegoke, 1969, p. 122, pl. 4, fig. 10.
Original description.--"Shell small, trigonal, equivalve, inequilateral, almost a quadrant of a spheno-discoidal solid; valves convex, inflated; beaks prominent, elevated, curved inward and forward; the forward dorsal margin slightly concave; posterior, slightly convex or straight; basal margin circular; ends sharply rounded, the anterior usually more so than the posterior; surface showing only concentric lines of growth which disappear on the earlier portions of the shell; a prominent ridge or angulation extending from the beaks diagonally to the posterior extremity; hinge typical of this genus; muscular impressions inaccessible."
Holotype.--CAS 131 (69.01, new number).
Type locality.--CAS 69. "S and W slopes of Pyramid Hills, 15 mi [24 km] NE of Bakersfield, [sec. 15, R. 28 S., R. 29 E.], Kern County, Calif. Jewitt Sand, Miocene (Keen and Bentson, 1944).
Occurrence in California.--Oligocene and Miocene: Temblor (Loel and Corey, 1932; Adegoke, 1969) and Vaqueros (Loel and Corey, 1932) Formations; Miocene: Jewitt Sand (Keen and Bentson, 1944) and Round Mountain Silt (Keen, 1943).
Mactromeris? montereyana (Arnold)
Plate 5, figure 9; Plate 5; Plate 5 caption
Mactra monteryana Arnold, 1908, p. 381, pl. 35, fig. 2; 1909, pl. 35, fig. 2. Packard, 1916, p. 311. Adegoke, 1969, p. 122-123.
Mactra (?) montereyana Arnold. Packard, 1916, p. 311.
Original description.--"Shell attaining a length of at least 30 mm.; width a little more than one-half length, subtrigonal, compressed, subequivalve, inequilateral; umbones a little behind middle, small, turned slightly forward; anterior margin considerably longer than posterior; very gently convex; anterior extremity quite sharply angulated below; a faintly developed carina or angle, most prominent near umbo, extends from the latter to the anterior extemity; base only very slightly rounded; posterior dorsal margin nearly straight, sloping only moderately steeply, posterior extremity regularly rounded and situated nearly midway between base and umbo; surface sculpture by numerous fine incremental lines and numerous obsolete short undulations. The dimensions of the type are: length, 31 mm., height, 18 mm., convexity, 2 mm."
Holotype.--USNM 165463.
Type locality.--"Love Creek, 1 mi [1.6 km] above confluence with San Lorenzo R., [SE 1/4, sec. 33, T. 9 S., R. 2 W.] Santa Cruz Quad", California. Monterey Formation, Miocene.
Comparison.--"This species [monereyana] may be distinguished from all others of the same genus from the west coast by its great relative length and long, attenuated anterior extremity. It is very closely allied to M. dolabariformis Conrad***but may be distinguished from the latter by its relatively greater length, less steeply sloping posterior dorsal margin, more central posterior extremity, and more attenuated anterior end." (Arnold, 1908, p. 381)
Occurrence in California.--Oligocene and Miocene: Temblor Formation (Adegoke, 1969); Miocene: Monterey Formation (Arnold, 1908).
Mactromeris? trampasensis (Packard)
Plate 5, figure 11; Plate 5; Plate 5 caption
Mactra trampasensis Packard in Clark, 1915, pl. 60, fig. 9.
Mactra trampasensis Packard, 1916, p. 282-283, pl. 13, fig. 3; pl. 16, figs. 1, 2.
Original description.--"Shell medium-sized, very ventricose, trigonal to subovate, nearly as high as long, and nearly equilateral; sculptured by faint distant concentric lines; beaks prominent, incurved, distant; posterior dorsal slope somewhat concave, with an ill-defined escutcheon; anterior dorsal slope concave, marked by a well-defined impressed lunule; anterior and posterior extremities about equally rounded, ventral margin broadly rounded. Hinge plate narrow; chondophore deep, nearly circular in outline, slightly overhung by the cardinal, probably roofed by a spur; left cardinal arms heavy; anterior arm slightly longer than the posterior, reaching from the dorsal margin of the shell to the ventral margin of the hinge plate; right cardinal partially destroyed; anterior arm strong, low, apparently confluent with the ventral lamina; laminae smooth; anterior lateral confluent with the anterior arm of the cardinal; posterior lamina low, long. Pallial line is unknown. The dimensions of the type specimen are: length 48 mm., height 38 mm., convexity 14 mm."
Holotype.--UCMP 11499.
Type locality.--UC 1237. "Top of knob about one-quarter of a mile [0.4 km] south-east of Burton's and about one and one-half miles [2.4 km] north of Los Trampas Creek, Concord Sheet, Contra Costa County, California." San Pablo Group, Miocene.
Comparison.--"The distinctive shape readily separates this species from other Pacific coast Mactrinae. The few specimens that are known show but little variation in general shape." (Packard, 1916, p. 282)
Occurrence in California.--Miocene: Neroly Sandstone, San Pablo Group (Weaver, 1949).
Mactromeris? beali (Hall and Ambrose)
Plate 5, figure 10; Plate 5; Plate 5 caption
Mactra beali Hall and Ambrose, 1916, p. 80. Wiedey, 1929, pl. 1, fig. 3.
Original description.--"Left valve. Shell trigonal, thin, slightly ventricose, inequilateral; umboes prominent; beaks not prominent, situated slightly posterior to middle of shell, anterior margin slightly curved upward, running to anterior extremity where it is sharply rounded; posterior margin practically straight, running to posterior extremity where it is angularly truncated; basal margin regularly curved; posterior and anterior margin make an angle of 105° at the beak; surface smooth."
Holotype.--CAS/SU 507; CAS 66544.01, new number.
Type locality.--Pleasanton Quadrangle, Alameda County, Calif. Monterey Formation, Miocene.
Occurrence in California.--Miocene: Monterey Formation (Hall and Ambrose, 1916).
Mactromeris? subquadrata (Clark)
Plate 12, figure 4; Plate 12; Plate 12 caption
Spisula subquadrata Clark, 1925, p. 102, pl. 17, fig. 3.
Original description.--"Shell large, fairly heavy, subquadrate in outline, beaks fairly prominent, strongly inturned, situated only a little posterior to anterior end; anterior dorsal edge, sloping steeply and abruptly away from beaks, forms approximately a right angle with posterior slope; anterior dorsal edge gently convex, merging gently with broad anterior end; posterior dorsal edge long, straight; posterior end broadly and regularly rounded. Surface smooth except for somewhat heavy incremental lines; dorsal margins strongly depressed and noticeably excavated on both sides of beaks. Hinge plate not exposed. Dimensions: Length about 74 mm.; height about 60 mm.; diameter of both valves 35 mm."
Holotype.--UCMP 30344.
Type locality.--UC 1131. Contra Costa County, Calif. San Ramon Formation, Miocene(?).
Supplementary description.--"This species is unique in its semiquadrate outline." (Clark, 1925, p. 102.
Comparison.--"S. subquadrata***differs decidedly from S. occidentalis in outline, the beaks are more conspicuous, and the shell is heavier." (Clark, 1925, p. 102)
Occurrence in California.--Miocene(?): San Ramon Formation (Clark, 1925).
Mactromeris? coalingensis (Arnold)
Plate 9, figure 10; Plate 9; Plate 9 caption
Mactra coalingensis Arnold, 1910, p. 71, pl. 25, fig. 4.
Mactra? coalingensis Arnold. Woodring and others, 1940, p. 93, pl. 33, fig. 1.
Spisula coalingensis (Arnold). Packard, 1916, p. 301-302, pl. 27, fig. 8.
"Spisula" coalingensis (Arnold). Adegoke, 1969, p. 122.
Original description.--"Shell averaging about 52 millimeters in width, equivalve, trigonal in outline, rounded behind, slightly attenuated in front; beaks not prominent, situated slightly anterior to middle of shell; anterior superior margin only slightly excavated in front of beaks, nearly straight to anterior extremity, which is quite abruptly truncated; posterior inferior margin slightly curved, and merging imperceptibly into the regularly convex posterior extremity; basal margin moderately curved. Hinge and cartilage areas concealed in the type, but believed to be similar to M. falcata Gould. The dimensions of the type are: length, 65 mm., height, 52 mm."
Holotype.--USNM 165513.
Type locality.--Waltham Creek Valley, south of Coalinga, Fresno County, Calif. Etchegoin Formation, Pliocene and Pliocene.
Comparison.--"This species is larger, relatively broader and more trigonal than S. falcata. It differs from S. brevirostrata in being more nearly equilateral and from S. albaria in being less ventricose." (Packard, 1916, p. 302)
Occurrence in California.--Pliocene: San Joaquin Formation (Adegoke, 1979); Pliocene and Pleistocene: Etchegoin Formation (Arnold, 1910; Woodring and others, 1941).
"Mactra (Harvella) elegans Sowerby" of Yates
Plate 6, figure 12; Plate 6; Plate 6 caption
Mactra (Harvella) elegans Sowerby. Yates, 1903, pl. 8, fig. 15.
Not Mactra (Harvella) elegans Sowerby, 1825.
Comments.--The specimen figured by Yates (CAS 2828; 66543.01, new number) is a Chione as noted by Keen and Bentson (1944, p. 64).
"Spisula granti Wiedey"
Spisula granti Wiedey, 1928, p. 152-153, pl. 20, figs. 2, 3.
Comments.--This species is a Crassatella. (See pl. 1, figs. 4, 5; Plate 1; Plate 1 caption).
Genus STEREOMACTRA Stewart, 1930
"Like Scissodesma but shell larger, heavier, laterals longer; resilium shallow." (Moore, 1969, p. N604)
Geographic range.--Western North America.
Geologic range.--Miocene and Pliocene.
Stereomactra abscissa (Gabb)
Plate 12, figures 1, 6; Plate 12; Plate 12 caption
Schizodesma abscissa Gabb, 1869, p. 20, pl. 4, figs. 34, 34a. Arnold, 1910, p. 130, pl. 12, fig. 3.
Spisula abscissa (Gabb). Clark, 1915, pl. 58, fig. 3. Not Packard, 1916, p. 289-290, pl. 23, fig. 4; pl. 24, fig. 2.
"Spisula" abscissa (Gabb). Adegoke, 1969, p. 121.
Spisula (Stereomactra) abscissa (Gabb). Stewart, 1930, p. 210-211, pl. 16, fig. 6.
Original description.--"Shell large, thick, irregularly subquadrate; beaks large, prominent, pointed forwards, nearly central; anterior end obliquely truncated; base broadly rounded; posterior end very strongly and abruptly truncated, the truncation ending at an angular ridge which passes from the beaks to the posterior basal angle. Surface marked by rough irregular lines of growth. Hinge composed of large robust teeth; lateral teeth long and thick."
Holotype.--ANSP 4548.
Type locality.--South of Martinez [Contra Costa County], Calif. Etchegoin Formation, Miocene and Pliocene.
Supplementary description.--"The hinge plate is rather broad, chondophore wide and deep, slightly overhung by the arm of the cardinal; left cardinal rather small, arms of equal length, extending ventrally to about the middle of the hinge plate; laterals long and rather thin, smooth, flat-topped, distant from the beak, the anterior one not reaching to the arm of the cardinal. Hinge of right valve unknown." (Packard, 1916, p. 289)
"The laterals are long and massive. The central cardinal is reduced and overlapped by the anterior cardinal which projects above the other two. The ligament was wholly internal. The dorsal posterior margin is broken away. The lunule is not inscribed. The posterior umbonal ridge is very prominent." (Stewart, 1930, p. 211)
Occurrence in California.--Miocene: San Pablo Group (Packard, 1916); Miocene and Pliocene: Etchegoin Formation (Keen and Bentson, 1944; Adegoke, 1969).
Genus SIMOMACTRA Dall, 1894
"Outline flattened cuneiform, inequilateral; pallial sinus smaller than in M. (Mactrotoma), siphonal gape small. (Moore, 1969, p. N598)
"Chondrophore slightly projecting, if at all. More compressed than Macrotoma. External and internal portions of ligament sharply divided by a shelly plate or ventral margin of nymph in some; three cardinal teeth present in each valve. Pallial sinus not confluent with pallial line. Lateral teeth pustulose on their dorsal surface." (Coan, Scott, and Bernard, 2000, p. 458)
Geographic range.--Western North America to Central America.
Geologic range.--Miocene to Holocene.
Simomactra falcata falcata (Gould)
Plate 10, figure 2; Plate 10; Plate 10 caption
Mactra falcata Gould, 1850, p. 216.
Mactra (Spisula) falcata Gould. Arnold, 1903, p. 176-177, pl. 19, fig. 1. Grant and Gale, 1931, p. 396-397.
Spisula falcata (Gould). Packard, 1916, p. 297-298, pl. 26, figs. 1a, 1b, 1c. Oldroyd, 1924, p. 195, pl. 20, figs. 1-3. Grant and Gale, 1931, p. 396.
Simomactra falcata (A.A. Gould 1850). Coan, Scott, and Bernard, 2000, p. 458, pl. 97.
Original description.--"The shell of this species is small, subtrigonal, slightly inequilateral. The beaks are small, sharply pointed and situated a little posterior to the middle of the shell; anterior dorsal edge nearly straight; posterior edge somewhat convex; base gently arcuate; anterior extremity somewhat attenuated, posterior evenly rounded. Hinge plate rather wide, chondophore shallow, apically roofed and overhung by the posterior arms of the cardinals; spur prominent; left cardinal fragile, compressed, the anterior arm much longer than the posterior, which markedly overhangs the resilifer; anterior arm of the right cardinal the heavier, bearing anteriorly a small lamella; laterals rather short, smooth, arising from the ventral margin of the hinge plate at a point distant from the umbones; laminae short, low and rather heavy, the dorsal ones arising from the dorsal shell margin; a prominent lamella occurs in the left valve between the anterior lateral and the cardinal, being parallel to and nearly equal in height to, the latter. Pallial sinus shallow, irregularly rounded. The dimensions of the specimen figured in this paper are: length, 43 mm., height 31 mm., convexity, 7 mm."
Holotype.--USNM 5893.
Type locality.--Puget Sound, Washington. Holocene.
Comparison.--"This species [falcata] superficially resembes S. brevirostrata, from which it has been recently separated. It differs from that new species in being more elongate and in possessing the compressed left cardinal characteristic of the subgenus Symmorphomactra, also in many minor details of the hinge. It might also be mistaken for S. planulata, from which it differs in being more ventricose and more equilateral, besides possessing a different type of left cardinal" (Packard, 1916, p. 297-298)
Occurrence in California.--Miocene: Briones (Trask, 1922), Cierbo and Neroly Sandstones, San Pablo Group (Weaver, 1949; Hall, 1960); Miocene and Pliocene: Tahana Member, Purisima Formation (Addicott, 1969); Pleistocene: Unnamed strata in southern California (Kanakoff and Emerson, 1959).
Habitat.--In the low intertidal zone to 50 m, on sandy substrata (Coan, Scott, and Bernard, 2000, p. 458). Living British Columbia to Isla San Martin, Baja California Norte.
Simomactra falcata brioniana (Trask)
Plate 10, figure 6; Plate 10; Plate 10 caption
Spisula falcata brioniana Trask, 1922, p. 152, pl. 4, figs. 2a, b.
S. falcata (Gould). Schenck and Keen, 1940, pl. 44, figs. 3, 4. Not Mactra falcata Gould, 1850).
Original description.--"Shell small to medium in size, subtrigonal, inequilateral, equivalve; beaks rather inconspicuous, incurved and only slightly prosogyrous; anterior dorsal edge long and straight; posterior dorsal edge straight to gently convex, and about two-thirds the length of the anterior dorsal edge; posterior end, evenly rounded; anterior ventral end produced and subacutely rounded; surface smooth except for fine incremental lines; hinge plate short, resilifer shallow; cardinals small and fragile; laterals very short and close to laminae."
Holotype.--UCMP 12380.
Type locality.-UC 3522. Concord, Quad., Contra Costa County, Calif. Briones Sandstone, San Pablo Group, Miocene.
Comparison.--"This variety [brioniana] resembles S. falcata (Gould),***but it differs from the latter in that it is higher in proportion to length; it possesses a more prominent umbonal ridge; it has a shorter hinge plate and shorter laterals; and the distance from the center of the hinge plate to the distal ends of the laterals is about one-half of what it is in S. falcata." (Trask, 1922, p. 152)
Occurrence in California.--Miocene: Briones Sandstone, San Pablo Group (Trask, 1922).
Subfamily LUTRARIINAE
Genus LUTRARIA Lamarck 1799
"Elongate, thin, gaping at each end; ligament short; no lunule or escutcheon." (Moore, 1969, p. N604)
Geographic range.--Cosmopolitan.
Geologic range.--Miocene to Holocene.
Genus LUTRARIA?
Lutraria? traskei Conrad
Plate 10, figure 4; Plate 10; Plate 10 caption
Lutraria traskei Conrad, 1855, p. 14; 1857, pl. 3, fig. 23 [not fig. 30 as stated, Keen and Bentson, 1944, p. 59].
Lutraria? traskei Conrad. Keen and Bentson, 1944, p. 59.
Original description.--"Suboval, ventricose, inequilateral, hinge and basal margin nearly parallel; posterior margin subtruncated and slightly oblique, or approaching a direct outline, posterior extremity rounded."
Holotype.--USNM 1848.
Type locality.--Carmelo, Monterey County, Calif. Miocene(?).
Occurrence in California.--Miocene(?): Monterey Formation?
Genus TRESUS Gray, 1853
"Large, ovate, ventricose, gaping posteriorly; hinge teeth small, resilifer large; ligament separated from resilium by shelly plate." (Moore, 1969, p. N604-605)
"Shell ovate to elongate, ventricose, with a posterior gape.*** Resilium separated from external ligament by shelly plate. Chondrophore projecting. Two cardinal teeth in each valve; lateral teeth small. Shell thickness varies with habitat, bay-dwelling specimens being more thin-shelled than those from offshore. Pallial sinus deep, broad." (Coan, Scott, and Bernard, 2000, p. 460)
Geographic range.--Western North America and eastern Asia.
Geologic range.--Miocene to Holocene.
Tresus saxadomoides (Clark)
Plate 12, figure 5; Plate 12; Plate 12 caption
Spisula? saxadomoides Clark, 1918, p. 159, pl. 16, fig. 1.
Original description.--"Shell medium in size, broadly elongate-ovate; beaks fairly prominent, strongly inturned, situated about two-thirds the distance from the posterior to the anterior end; anterior dorsal margin slightly excavated; anterior end rather strongly produced, broadly and regularly rounded; posterior end broadly and regularly rounded; posterior dorsal margin long, nearly straight. Ventral edge gently arcuate. Surface smooth except for incremental lines; anterior and posterior dorsal margins of shell rather strongly pouting, one of the common characteristics of many of the species of this genus. Hinge plate of left valve only imperfectly exposed, showing a small deltoid cardinal with a deep resilifer pit."
Holotype.--UCMP 11268.
Type locality.--UC 1131. Contra Costa County, Calif. San Ramon Formation, Miocene(?).
Occurrence in California.--Miocene(?): San Ramon Formation (Clark, 1918).
Tresus nuttallii (Conrad)
Lutraria (Cryptodon) nuttallii Conrad, 1837, p. 235, pl. 18, fig. 1.
Schizothaerus nuttallii Conrad. Conrad, 1853, p. 199. Clark, 1915, p. 420, pl. 59, fig. 2. Martin, 1916, p. 254. Packard, 1916, pl. 35, figs. 1a, 1b. Packard, 1918, p. 283, pl. 28, figs. 1a, 1b. Grant and Gale, 1931, p. 404-405, pl. 22, fig. 9; pl. 23, figs. 8a, 9.
Tresus nuttalli (Conrad). Keen, 1962, p. 178-179. Addicott, 1963, p. 143-145, 3 text figs. Adegoke, 1969, p. 123. Hertlein and Grant, 1972, p. 318, pl. 54, fig. 11; pl. 55, figs. 9, 13, 14, 17. Morris and others, 1980, p. 379-380, fig. 15.48.
Tresus nuttalli (Conrad, 1837). Coan, Scott, and Bernard, 2000, p. 463-464, pl. 98.
Original description.--"Shell elliptical, slightly gibbous from beak to base; posterior side produced; ligament margin slightly declining, rectilinear, extremity obliquely subtruncated; umbo prominent; colour white; epidermis very thin, brown, wrinkled on the margins. Length, six inches."
Holotype.--BM(NH) 61.5.30.134.
Type locality.--"Inhabits salt marshes, bare at low water, in the vicinity of Sta. Barbara." California, Holocene.
Supplementary description.--"Shell ovate-elongate, longer posteriorly and more evenly curved ventrally than
Comparison.--"The shell of Tresus nuttallii is larger, longer, more ventricose, the anterior end is longer and the posterior gape is more rounded than that of Tresus pajaroanus Conrad, a Pliocene species originally described from***the Purisima Formation.
"The shell of the Japanese species [Schizothaerus keenae Kuroda and Habe] is higher and the posterior truncation is broader than that of T. nuttallii." (Hertlein and Grant, 1972, p. 318)
Occurrence in the Californias.--Miocene: Pancho Rico (Durham and Addicott, 1965); San Pablo Group (Clark, 1915) and Topanga Formations (Takeo Susuki, written commun., 1987); Miocene and Pliocene: Etchegoin (Adegoke, 1969), Tahana Member, Purisima (Addicott, 1969) and Towsley (Kern, 1973) Formations; Pliocene: San Diego (Hertlein and Grant, 1972) and San Joaquin (Adegoke, 1969) Formations; Pliocene and Pleistocene: Merced (Yancey, 1978) and Saugus (Givens, 1991) Formations; Pleistocene: unnamed strata at Potrero Canyon (Valentine, 1956), San Diego (Moore, 1968), Baja California Norte (Valentine, 1957; Addicott and Emerson, 1959; Valentine and Rowland, 1969), and Baja California Sur (Emerson, 1980).
Habitat.--"Common, burrowing to depths of 1 m or more in firm to loose sandy mud, low intertidal zone in bays and on sheltered bottoms offshore to 30 m depth***
"Young animals inhabit the upper layers of the substratum and they can burrow actively. Older individuals live deeper, and those over 60 mm long are very slow burrowers. However, the larger animals tend more and more to orient their shells at an angle to the siphons and thus become more firmly anchored basally." (Morris and others, 1980, p. 379)
Living Alaska to Baja California Sur.
Tresus pajaroanus (Conrad)
Venus pajaroana Conrad, 1857, p. 192, pl. 4, figs. 1, 2.
Schizothaerus pajaroanus (Conrad). Dall, 1909, p. 130. Peck, 1960, p. 237, pl. 21, fig. 12
Schizothaerus nuttallii (Conrad) variety pajaroanus (Conrad). Grant and Gale, 1931, p. 405-406, pl. 22, figs. 6a, b, 8. Weaver, 1942, p. 249, pl. 58, fig. 10.
Tresus pajaroanus (Conrad). Adegoke, 1969, p. 123, pl. 7, fig. 5.
Original description.--"Obliquely ovate-obtuse, ventricose, very inequilateral; anterior margin obtusely rounded, posterior side sub-cuniform; posterior end truncated obliquely inward."
Holotype.--USNM 13318.
Type locality.--Pajaro River, Santa Cruz, Calif. Santa Cruz County, Calif. Purisima Formation, Miocene and Pliocene.
Supplementary description.--"Tresus pajaroanus is most inflated anteriorly, compressed posteriorly, with a narrow posterior dorsal slope***Growth lines crossing the posterior dorsal slope are not sinuous." (Roth, 1979, p. 325)
Comparison.--"Tresus pajaroanus differs from Tresus nuttallii ***in being smaller, with a short anterior end, somewhat wedge-shaped outline, and rounded, not truncated, posterior end. Only a narrow siphonal gape is present." (Roth and Talmadge, 1975)
Occurrence in California.--Miocene and Pliocene: Etchegoin (Adegoke, 1969), Purisima (Perry 1988) and Tahana Member, Purisima (Addicott, 1969); Pliocene: San Joaquin Formation (Adegoke, 1969); Pliocene and Pleistocene: Fernando(?) Formation (Kennedy, 1975) and Merced Formation (Weaver, 1949).
Subfamily PTEROPSELLINAE Keen, 1969
Genus RAETA Gray, 1853
"Resembling Anatina, but more convex, compressed posteriorly, sculpture of concentric plications; dorsal margin not reflected." (Moore, 1969, P. N606)
Geographic range.--Europe, eastern and western North America, central and South America.
Geologic range.--Eocene to Holocene.
Genus RAETA?
Raeta? plicatella longior (Grant and Gale)
Plate 12, figures 2, 3; Plate 12; Plate 12 caption
Anatina (Raeta) plicatella (Lamarck) variety longior Grant and Gale, 1931, p. 408-409, pl. 23, figs. 1a, 1b.
Original description.--"Shell like that of Anatina plicatella Lamarck but more elongate, less ventricose, with the posterior end more constricted, and an almost straight anterior dorsal margin. Length, 40 mm., height, 25 mm., convexity (left valve), about 8mm."
Holotype.--SDNM 192.
Type locality.--Superior Oil Co. well, Ansolabehere No. 1, in sec. 9, T. 29 S., R. 27 E., Mt. Diablo B. and M., depth, 4525-7 feet, near Bakersfield, Kern County, [upper Fruitvale Sand] Calif. Miocene.
Comparison.--"This specimen [longior] is more elongate, has a more constricted posterior end, and more posterior beaks than Conrad's transmontana.
"A. transmontana has approximately central beaks and fine, somewhat discontinuous, concentric sculpture. In the variety longior the umbo is a little more than a third of the total length of the shell from the posterior end." (Grant and Gale, 1931, p. 213)
Occurrence in California.--Miocene: Unnamed sediments (Grant and Gale, 1931).
Raeta? transmontana (Conrad)
Plate 12, figure 7; Plate 12; Plate 12 caption
Lutraria transmontana Conrad, 1856, p. 315; 1857, p. 194, pl. 5, fig. 6.
Anatina (Raeta) transmontana (Conrad). Grant and Gale, 1931, p. 409, pl. 22, fig. 2.
Original description.--"Longitudinally ovate-triangular, inequilateral, thin; anterior end and base regularly rounded; posterior side cuneiform, extremity rounded; summits prominent; surface concentrically indented or subplicated; umbonal region concentrically plicated; plicae irregular."
Holotype.--USNM 13322.
Type locality.--"Rancho Triumpho, Los Angeles" [California]. Grant and Gale, (1931, p. 409) give the locality as "Rancho Triumfo near the boundary between Los Angeles and Ventura counties, probably in the Topanga formation***".
Supplementary descripton.--"This species [transmontana] has approximately central beaks and numerous concentric growth lines." (Grant and Gale, 1931, p. 409)
Ocurrence in California.--Miocene(?): Topanga Formation(?) (Grant and Gale, p. 409).
[Last updated June 28, 2002.]
To title page of Tertiary Marine Pelecypods
of California and Baja California
OJ QJ I h p w x ?
T > .
F
G
w
I h p w x ?
T > .
F
G
w
Z
K
L
+ | [ \ @ h L R S A B > g I / | e
Z
K
L
+ | [ \ @ h L R S A B > g I / | b > Y Z 4 b > Y Z 4 b ` ? I b c 2 x y %! s! ! " W" " " 9# # # $ l$ $ % M% % % % & & M& & & & & ;' ' ' ' ' N( ( ( ( ( %) J) K) ) ) )
* 0* 1* * * + j+ + + B, , , +- w- - - - - ,. e b ` ? I b c 2 x y %! s! ! ! " W" " " 9# # # $ l$ $ % M% % % % & & M& & & & & ;' ' ' ' ' N( ( ( ( ( ( %) J) K) ) ) )
* 0* 1* * * + j+ + + B, , , +- w- - - - - ,. w. ,. w. . /
/ U/ / / 60 0 0 0 0 P1 t1 u1 1 1 1 &2 '2 p2 2 2 2 F3 b3 c3 3 3 4 4 S4 T4 4 4 4 4 5 5 P5 5 5 26 }6 6 6 6 C7 d7 e7 7 7 F8 x8 y8 8 9 X9 9 9 8: : : $; s; ; < O< [< \< < < == = = = = G> > > ? ? Z? [? ? ? ? @ 5@ 6@ @ @ @ @ @ @ DA VA WA A A ew. . /
/ U/ / / 60 0 0 0 0 P1 t1 u1 1 1 1 &2 '2 p2 2 2 2 F3 b3 c3 3 3 4 4 4 S4 T4 4 4 4 4 5 5 P5 5 5 26 }6 6 6 6 C7 d7 e7 7 7 F8 x8 y8 8 9 X9 9 9 9 8: : : $; s; ; < O< [< \< < < == = = = = G> > > ? ? Z? [? ? ? ? @ @ 5@ 6@ @ @ @ @ @ @ DA VA WA A A >B B B .C sC tC C C C 4D iD jD D E KE WE A >B B B .C sC tC C C C 4D iD jD D E KE WE XE E E =F HF IF F F F F F :G qG rG G G H %H &H zH H I \I I I HJ J J 'K sK K L PL L L 4M M M N
N 2N 3N N N O JO KO O O *P {P P P P *Q rQ }Q ~Q Q Q Q Q 5R ZR [R R R R S aS S S >T T T U ,U -U PU QU U U 2V 3V V eWE XE E E =F HF IF F F F F F :G qG rG G G H %H &H zH H I \I I I HJ J J 'K 'K sK K L PL L L 4M M M N
N 2N 3N N N O JO KO O O *P {P P P P *Q rQ }Q ~Q ~Q Q Q Q Q 5R ZR [R R R R S aS S S >T T T U ,U -U PU QU U U 2V 3V V V W V V W #W $W lW W
X 0X 1X X X X X X Y \Y Y Y Y 5Z 6Z jZ kZ Z Z Z [ [ [[ \[ [ [ 9\ \ \ ] h] ] ^ P^ j^ k^ ^ ^ ^ _ _ P_ _ _ 7` ` ` a ma a b b b Zb b b b c :c ;c tc uc c c c 2d 9d :d d d e je e e Gf f f *g tg g h $h %h Jh Kh h h -i 9i :i i i j (j )j eW #W $W lW W
X 0X 1X X X X X X Y \Y Y Y Y 5Z 6Z jZ kZ Z Z Z [ [ [[ \[ [ [ [ 9\ \ \ ] h] ] ^ P^ j^ k^ ^ ^ ^ _ _ P_ _ _ 7` ` ` a ma a b b b Zb Zb b b b c :c ;c tc uc c c c 2d 9d :d d d e je e e Gf f f *g tg g h $h %h %h Jh Kh h h -i 9i :i i i j (j )j sj j
k &k 'k Nk Ok k k k k 0l Ul Vl l l l )j sj j
k &k 'k Nk Ok k k k k 0l Ul Vl l l l l Am Bm m m m n bn n n Go o o +p xp p q [q q q q q Cr `r ar r r Cs s s *t zt t t t t t .u /u xu u u u v v fv v v Hw w w +x }x x y Ay By gy hy y z Kz Wz Xz z z 7{ I{ J{ { { { { 4| 5| }| | | | :} Q} R} } } el l Am Bm m m m n bn n n Go o o +p xp p q [q q q q q Cr `r ar r r Cs s s s *t zt t t t t t .u /u xu u u u v v fv v v Hw w w +x }x x y Ay By gy gy hy y z Kz Wz Xz z z 7{ I{ J{ { { { { 4| 5| }| | | | :} Q} R} } } } ~ b~ } } ~ b~ ~ ~ D " r
T ' ( r N c ! _ ` օ ׅ # G H ߆ - | Ƈ ] P ; ? @ P 5 Ǎ W J ֏ h D m n U V eb~ ~ ~ D " r
T ' ( r N c ! _ ` օ ׅ # G H ߆ - | Ƈ ] P ; ? @ P 5 Ǎ W J ֏ h D m n U V Ȓ ɒ % & o T 0 | ȕ _ V Ȓ ɒ % & o T 0 | ȕ _ і Җ f ї d 5 ͙ R S 2 \ ] ՛ ֛ & ' t ] C ٞ & o T ؠ ٠ D ϡ С f A ܣ ݣ + n o ` i j 4 V W 7 e і Җ f ї d 5 ͙ R S 2 \ ] ՛ ՛ ֛ & ' t ] C ٞ & o T ؠ ٠ D ϡ С f A ܣ ݣ + n o ` i j 4 V W 7 ҧ f 7 ҧ f ' ( z ȩ a B ٫ ' W X : ͭ ٭ ڭ & r
S ӯ ԯ % p 6 ` a L L y z ij г ѳ 9 : д c ѵ ҵ y z ƶ ^ B Ը # n ¹ ߹ - x º \ ; Ӽ + ef ' ( z ȩ a B ٫ ' W X : ͭ ٭ ڭ & r
S ӯ ԯ % p 6 ` a L L y z ij г ѳ ѳ 9 : д c ѵ ҵ y z ƶ ^ B Ը # n ¹ ߹ - x º º \ ; Ӽ + ҽ ӽ A B ξ Ͼ O P : + ҽ ӽ A B ξ Ͼ O P :
L M R > O . x , - v l T 3 ~ O ^ f z { - . i j 2 } N e
L M R > O . x , - v v l T 3 ~ O ^ f f z { - . i j 2 } N i H i H 0 } \ ] @ $ o
W b B D + z B C U { | c G # l H & \ ] m ! j 7 c d ^ ! C e 0 } \ ] @ $ o
W b B D + z B C U { | c G # l l H & \ ] m ! j 7 c d ^ ! C D F H Q R 0 z C D F H Q R 0 z
Y 9 g
_ ` > u v U B t u T h _ ? " k J ) t u / y / 0 { * z e
Y 9 g
_ ` > u v U B B t u T h _ ? " k J J ) t u / y / 0 { * z b ~ b ~ d K - |
3 4 ~ @ A 4 H I v w L M P : ; P 2 { T j
>
?
_ 3 4 }
p
O 3 { e d K - |
3 4 ~ @ A 4 H I v w w L M P : ; P 2 { T T j
>
?
_ 3 4 }
p
O 3 { ^ > J o p M } ~ _ ^ > J o p M } ~ _ E ' V W / z _ > ! l 2 ! m a z { % & i j O X Y ^ :! ! ! " f" " " D# # # # # # # I$ $ e E ' V W / z _ > ! l 2 ! m a z { % & i j O X Y Y ^ :! ! ! " f" " " D# # # # # # # I$ $ $ (% v% % & U& & $ $ (% v% % & U& & & 5' ' ' ' ' ;( ( ( ) 9) :) ) ) * p* * +
+ ^+ + + , , M, r, s, , - - T- - - .. {. . / U/ V/ / / / / / 40 0 0 0 0 0 1 1 M1 N1 1 1 1 2 2 Q2 2 2 3 3 Q3 R3 3 3 3 4 4 4 V4 W4 4 4 4
5 5 Y5 `5 a5 5 5 K6 6 6 6 6 6 G7 g7 h7 7 e& & 5' ' ' ' ' ;( ( ( ) 9) :) ) ) * p* * +
+ ^+ + + , , M, r, s, , - - - T- - - .. {. . / U/ V/ / / / / / 40 0 0 0 0 0 1 1 M1 N1 1 1 1 2 2 2 Q2 2 2 3 3 Q3 R3 3 3 3 4 4 4 V4 W4 4 4 4
5 5 Y5 `5 a5 5 5 K6 6 6 6 6 6 6 G7 g7 h7 7 7 J8 \8 ]8 8 8 8 9 9 k9 9 9 9 -: y: : : ; O; ; ; -< 7 7 J8 \8 ]8 8 8 8 9 9 k9 9 9 9 -: y: : : ; O; ; ; -< }< < = ]= = = >> > > '? o? ? @ X@ q@ r@ @ @ @ ,A uA A A A DB B B B C ZC C C ?D D D D E _E `E E E E F F ZF tF uF F
G VG G G ;H H H !I gI hI I I I I I ;J
