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[Please cite as follows: Moore, E.J., 2003, Family Donacidae, in Tertiary marine pelecypods of California and Baja California, Chapter G: http://www.cmug.com/~chintimp/Donacidae.htm, 4 p., 1 pl.]

Genus Donax Linné, 1758

“Shell elongate to ovate, frequently wedge-shaped, thick. Sculpture absent or radial riblets or punctae. Anterior end produced; posterior end short, truncate or rounded. Lateral teeth variable.” (Coan, Scott, Bernard, 2000, p. 422)

Donax latus Gabb, pl. 8, fig. 1 Plate 8; Plate 8 captions

Donax latus Gabb, 1869, p. 183, 238, pl. 30, fig. 75. Stewart, 1930, p. 205, pl. 8, fig. 5.

Original description.—“Shell broad, triangular, thin, very inequilateral; beaks high, placed about 2/5 of the length from the anterior end; sides sloping, nearly straight, a rounded angle running from the beaks to the posterior side; base broadly and pretty regularly convex, joining the other two sides of the triangle by narrowly rounded angles. Interior basal margin minutely dentate, the dentations corresponding with the exterior ribs. Surface ornamented by numberous fine, regular, radiating ribs, flattened on top, and with the interspaces somewhat narrower than the ribs.”

Holotype.—MCZ 15028.

Type locality.—Ten miles west of Griswold’s, southeast of the Sheep Well, on the road from San Juan to New Idria, Calif.

Supplementary description.—“This shell is remarkable for its thinness, and as much of the hinge as I have been able to expose, shares the delicate character of the shell itself.” (Gabb, 1869)

“The radiating ribs are distinct and fairly regular***The ligamental groove is short, shallow and close beneath the umbo.” (Stewart, 1930, p. 205)

Geographic range.—Middle California.

Geologic range—Eocene.

Occurrence in California.—Eocene: Domengine(?) (Stewart, 1930) and Tejon (Arnold,1906) Formations.

Donax scrippsensis M.A. Hanna, pl. 8, fig. 2 Plate 8; Plate 8 captions

Donax scrippensis M.A. Hanna, 1927, p. 293, pl. 40, figs. 1, 12.

Original description—“Left valve: shell of medium size, heavy; angle between the posterior and dorsal surfaces approximately a right angle (ninety-seven degrees); anterior dorsal angle rather sharply rounded; ventral margin regularly broadly rounded; posterior ventral angle more sharply rounded than the anterior dorsal; general shape roughly a 30-60 degree right triangle; anterior and dorsal surfaces flattened, forming prominent surfaces nearly normal to the plane of the shell; shell moderately well inflated; beak not extending beyond the dorsal posterior angle; ornamentation of the outer surface consists of fairly prominent growth lines and faint suggestions of radial ribbing; prominent radial ribbing on weathered specimens may be mistaken for true surface radial ribbing; hinge plate small, directly under the beak; two cardinals large, prominent, anterior one slightly bifid; laterals not exposed, if present; interior of the shell not exposed; inner margin crenulate. Dimensions: “Altitutde 13 mm., length 18 mm., diamenter 3.5 mm.”

Holotype.—UCMP 30992.

Type locality.—UC 5089. North of Scripps Institution pier 100 yards, elevation 10 ft., La Jolla Quad., San Diego County, Calif.

Comparison.—“Donax scrippsensis n.sp. differs from Donax latus Gabb in the much heavier shell, in the lack of radial sculpturing, and in the shape of the genral outline.” (M.A. Hanna, 1927, p. 293)

Geographic range.—Southern California.

Geolgoic range.—Eocene.

Occurrence in California.—Eocene: Rose Canyon Shale (Keen and Bentson, 1944).

Donax gouldii Dall, pl. 8, fig. 3 Plate 8; Plate 8 captions

Donax obesus Gould, 1851, p.90. Not Donax obesus d’Orbigny, 1846.

Donax gouldii Dall, 1921, p. 49. I.S. Oldroyd, 1924, p. 183, pl. 49 figs. 8, 9. Grant and Gale, 1931, p. 380, pl. 13, fig. 12. Coan, 1973b, p. 131-134, figs. 1-3, 7. Coan, 1983, p. 290-291, fig. 34. Coan, Scott, and Bernard, 2000, p. 423, pl. 88.

Donax (Serrula) gouldii Dall. Hertlein and Grant, 1972, p. 303, pl. 48, figs. 16, 19, pl. 57, fig. 8.

Original description.—“T. parva, solida, ovatocuneata, ventricosa, nitida, radiatim leviter striata, coloribus albidis et fulvidi somnino vel radiatiim picta et plerumque zonis violaceis ornata; angulo postero-dorsali rectangulari; facie posteriori cordiformi, subtriangulari; latere antico angustato, cito rotundato; margine ventrali denticulato, postice coarctato: intus albe, vel flavescens, violaceo nuberculata, ad maarginem dorsalem fuscata.” (obesus)

Holotype.—USNM 664935. (Coan, 1973, p. 132)

Type locality.—San Diego, Calif.

Supplementary description.—“Shell heavy, cuneate, inflated. Anterior end longer, posterior end abruptly truncate. Surface polished, but with obscure radial striae. Periostracum very thin, varnished. Shell buff or yellowish, frequently banded and maculated with brown or blue; inner margins crenulate. Length to 35 mm.” (Coan, Scott, and Bernard, 2000, p. 423)

Geographic range .—Living: southern California to Baja California Sur; fossil: southern California to Baja California Norte..

Geologic range.—Pliocene to Holocene.

Occurrence in the Californias.—Pliocene: San Diego Formation (Hertlein and Grant, 1972); Pliocene and Pleistocene: Fernando (Kennedy, 1975) and Saugus (Waterfall, 1929) Formations; Pleistocene: unnamed strata southern California (Kanakoff and Emerson, 1959) and Baja California Norte (Valentine, 1957).

Habitat.—“in the middle to low intertidal zone, to 5 m, in sand, usually on exposed foreshores.” (Coan, Scott, and Bernard, 2000, p. 423)

Donax? triangulata Anderson and Martin, pl. 8, fig. 4 Plate 8; Plate 8 captions

Donax triangulata Anderson and Martin, 1914, p. 63, pl. 3, fig. 9.

Keen and Bentston (1944, p. 47) assign this species to the genus Bornia.

Original description.—“Valves small, thin, trigonal, convex; beaks a little anterior to the middle; dorsal margins nearly straight; anterior extremity rounded; basal margin nearly straight; posterior end sharply rounded; an umbonal angulation extending from the beaks to the anterior and posterior extremities, forming areas sculptured with six or seven radial ribs; left valve with one cardinal and two lateral teeth; ends crenulated within; muscular impressions indistinct.”

Holotype.—CAS 130.

Type locality.—CAS 65. On west bank of a small canyon 1 1/4 miles northeast of Barker’s ranch house, Kern County, California. Round Mountain Silt.

Geographic range.—Southern California.

Geologic range.—Oligocene and Miocene.

Occurrence in California.—Oligocene and Miocene: Temblor Formation (Anderson and Martin, 1914).

Subgenus Paradonax Cossmann in Cossmann and Peyrot, 1910

“Elongate, slightly gaping anteriorly and posteriorly; posterior end short. Surface smooth, polished, with feeble radial striae on central slope” (Coan, Scott, and Bernard, p. 422, 2000)

Geographic range.—California to Peru.

Geologic range.—Oligocene to Holocene.

Donax (Paradonax) californicus Conrad, pl. 8, fig. 5 Plate 8; Plate 8 captions

Donax californica Conrad, 1837, p. 254, pl. 19, fig. 21. Dall, 1900, p. 968-969. Arnold, 1903, p. 170, pl. 13, fig. 9. Oldroyd, 1924, p. 7. Grant, and Gale, 1931, p. 379.

Donax (Paradonax) californicus Conrad. Coan, Scott, and Bernard, 2000, p. 422, pl. 88.

Original description.—“Shell elongated, somewhat pointed at both extremities; disks with very minute radiating lines; colour yellowish obscurely rayed; a brown stripe on the anterior and posterior submargin; within white and purplish brown; margin beautifully crenulated.”

Holotype.—

Type locality.—Coast near Santa Barbara, Calif.

Supplementary description.—Shell elongate-trigonal, thinner than Donax gouldii. Posterior end pointed; ventral margin with slight bend. Surface polished, with feeble radial striae. Periostracum varnished. Inner shell margin crenulate.***Length to 35 mm.” (Coan, Bernard, and Scott, 2000, p. 422)

Geographic range.—Living: Southern California to Peru; fossil: southern California to Baja California Norte.

Geologic range.—Pliocene to Holocene.

Occurrence in the Californias.—Pliocene and Pleistocene: San Pedro Formation (Arnold, 1903); Pleistocene: unnamed sediments at Bahía San Quintín (Grant and Gale, 1931).

According to Hertlein and Grant (1972, p. 303) “This species was recorded by both Cooper and Dall as occurring among the fossils from the San Diego well. We have not seen specimens of it in any collections from the San Diego Formation. It occurs commonly in Pleistocene beds in southern California and northern Lower California. It has not been recorded from strata of Pliocene age, so far as we know, by any modern author.”

[Donax? protexta Conrad=Solemya ventricosa Conrad]

[Last updated July 6, 2003.]

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