Cyclopecten martinezensis (Gabb, 1869)
GABB, W. M. 1866-1869. Paleontology of California. Vol II. Cretaceous and Tertiary fossils. Geological Survey of California, 299 p., pls. 1-36 [p. 198, pl. 33, fig. 96]
1869 Pecten martinezensis Gabb, 1869
W. M. Gabb, 1866-1899, plate 33.
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«SHELL minute, thin, elongate, equivalve, equilateral; sides straight above, below forming with the base a regular curve. Lower valve, right auricle deeply emarginate, narrow; left smaller. Upper valve, right auricle small; left large, margin slightly sinuous. Surface ornamented by numerous fine radiating ribs.»
Length from beak to base, .34 inch.
Not common in the Martinez Group, Martinez. From the other Pectens of the California Cretaceous, this species can be distinguished by its small size and radiating ribs. I was formerly inclined to believe it to be the young of P. Traskii, but have now three specimens varying only in size one or two-hundredths of an inch, and consequently cannot resist the belief that it is a distinct species.» WILLIAM MORE GABB, 1869
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«Lectotype.— MCZ 15026a.
Type locality.— Martinez [Contra Costa County], Calif. Martinez Formation, Paleocene. Comments.— On the basis of the lectotype and two remaining specimens in the type lot, this species is small, thin shelled, and has fine radiating ribs or striations. The lectotype is an internal mold that retains no shell. It is presumably a left valve and is moderately inflated for its size. Faint traces of ribs or striations are preserved near the ventral posterior margin. The anterior auricle is small and squarely truncated; the posterior auricle is incomplete but may have been slightly smaller. One specimen remaining in the type lot, also apparently a left valve, shows traces of fine ribs over the entire surface of the internal mold. The auricles are incomplete, retain patches of the internal shell layer, and are of the same size and proportions as those on the lectotype. The last remaining specimen in the type lot is an incomplete specimen that shows the interior of the shell. It seems to be a right valve and, if so, the anterior auricle was narrow and perhaps not very long. None of the specimens in the type lot show internal ribs. Thus the species is presumably neither Pseudamussium nor Parvamussium, and the valves do not show the posterior obliquity of Delectopecten. The fine radial ribs and outline of the auricles suggest Cyclopecten. Geographic range.— Middle California. Geologic range.— Paleocene. Occurrence in California.— Martinez Formation.» MOORE, E. J. 1984. Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae. United States Geological Survey Professional Paper, 1228-B: iv + B1-B112, figs. 1-2, pls. 1-42. [p. B9]
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Cyclopecten? martinezensis (Gabb ); E. J. Moore, 1984, Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae, plate 1, figures 9, 10.
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