Delectopecten lillisi (Hertlein, 1934)
HERTLEIN, L. G. 1934. New oysters and a new Pecten from the Tertiary of California. Bulletin of the Southern California Academy of Sciences, 33 (1): 1-5, pls. 1,2. [p. 5, pl. 1, fig. 1; pl. 2, figs. 2, 3]
1934 Pecten (Pseudamusium) [sic] lillisi Hertlein, 1934
L. G. Hertlein, 1934, plates 1, 2.
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«Shell small, of general form of Pecten pedroanus Trask; right valve, the anterior ear well defined, set off from the rest of the shell by a well defined groove, a well developed byssal notch is present; anterior ear ornamented by six or seven riblets. which are crossed by imbricating lines of growth; posterior ear unornamented except by fine lines of growth; the anterior portion of the valve ornamented by about ten fine spinose riblets; the posterior portion of the valve unornamented except by fine lines of growth; entire surface of valve covered by fine submicroscopic carnptonectes striations which cross the radiating riblets. Measurements of holotype, altitude 14.1 mm.; length (approximately) 13 mm.; length of hinge line 9.2 mm.
Left valve (paratype), the anterior ear is ornamented by about six to eight fine radial ribs; the surface of the valve is ornamented by fine radiating riblets; entire surface covered by camptonectes striations similar to the right valve. Holotype : No. 6062 and paratypes, Nos. 6063 and 6064 (C. A. S. type coll.) from Loc. 1874 (C. A. S.) diatomite, Kreyenhagen shale, from S. E. corner of Sec. 35, T.6 S., R.7 E., M. D. M., Stanislaus County, California; on the north side of Crow Creek road. Bedded material exposed in quarry, dip nearly flat. G. D. Hanna and J. A. Taff collectors. Kreyenhagen formation; upper Eocene or lower Oligocene. The holotype and paratypes are excellent impressions in the white diatomaceous shale. Pecten lillisi may be distinguished from P. pedroanus Trask and other fossil and Recent species of small pectens on the west coast of North America, by the small number of delicate spinose ribs which ornament the anterior portion of the right valve, and by the fine submicroscopic camptonectes striations which cover the surface of the shell. The less numerous ribs on the right valve distinguish the new species from Pecten (Pseudamusium) panamensis Dall.⁹ Compared to Pecten (Pseudamusium) reticulus Dall.¹º the new species differs in the shape of the ears and in the greater number of radiating riblets on the left valve; also the anterior portion of the right valve possesses more radiating riblets than the species described by Dall. No mention is made by Dall in the description, regarding the presence of any camptonectes striations on P. reticulus. Pecten (Pseudamusium) thalassinus Dall,¹¹ described but apparently unfigured, is said to be ornamented similar to P. reticulus but with the sculpture less pronounced. The strong spines on the ribs of the right valve, strongly, sculptured ears, and camptonectes striations of P. lillisi serve to distinguish it from Dall's species.» ⁹ Bull. Mus. Comp. Zool. vol. 43, no. 6, 1908, p. 404, pl. 6, figs. 8 and 10. "Gulf of Panama, in 322 fathoms, mud, bottom temperature 56º F." .... "ranging from near Acapulco, Mexico, to the Galapagos Islands, in 141 to 885 fathoms, soft bottom, temperature 37º. 2 to 53º. 5 F."
¹º Bull. Mus, Comp. Zool. vol. 12, no. 6, 1886, p, 221. pl. 5, flgs. 8 and 10. "Obtained in 82-123 fmis. at Barbados." ¹¹ Bull. Mus. Comp. Zool. vol, 12, no. 6, 1886, p. 221. "80 to 317 fms, off Martha's Vineyard," and "off Havana in 450 fms." LEO GEORGE HERTLEIN, 1934
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