Parvamussium cowperi (Waring, 1917)
WARING, C. A. 1917. Stratigraphic and faunal relations of the Martinez to the Chico and Tejon of Southern California. Proceedings of the California Academy of Sciences [4th Series], 7: 41-124, pls. 7-16. [p. 63, pl. 7, figs. 1, 2]
1917 Pecten (Propeamusium) [sic] cowperi Waring, 1917
C. A. Waring, 1917, plate 7.
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«This species is easily recognized as being closely allied to Gabb's Pecten interradiatus of the Eocene. The shell is small, subcircular, equivalve, equilateral, compressed, thin; upper valve, ears equal, moderately large; lower (right) valve, right ear long, deeply and narrowly emarginate; right valve with about nine large internal ribs, equally spaced, which are rounded and extend from the umbone nearly to the margin where they are abruptly truncated ; external surface ornamented with many fine equally spaced concentric lines; upper valve with four to eight rather large rounded internal riblets which extend from the umbone nearly to margins ; external surface marked by many fine radial ribs which are nearly obsolete near the anterior and posterior of the shell. Locality 2, L. S. J. U. Pal. Col.
This species has also been found by the writer in the Chico shales of the Tesla sheet. Probably the unnamed Pecten* allied to P. interradiatus from "Road cutting below Prof. Richer's house at mouth of Strawberry Canyon, Berkeley. Cutting now walled up. A. C. L. Cretaceous shale," belongs to this species. Named in honor of Dr. Andrew Cowper Lawson of the University of California.» * U. S. Geol. Surv. Prof. Paper No. 47, p. 54.
CLARENCE ALM WARING, 1917
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«Discussion. — Waring (1917) named Propeamussium (Parvamussium) cowperi without establishing a type specimen. The original? label that indicated "type spec." was housed with specimens CAS 61644.01 and CAS 61644.02, which are the two figured specimens of Waring (M. G. Kellogg, personal commun.). Stanford University cataloged these specimens as syntypes and an additional specimen (CAS 61644.03) as a topotype, which CAS later catalogued as a paratype. Specimens CAS 61644.04 and CAS 61644.05 (counterpart of CAS 61644.01) are plaster casts; the location of the original specimens is unknown. Although the author prefers to designate right valves as holotypes, the fragmentary nature of Waring's figured right valve (CAS 61644.01; PI. 7, fig. 2) makes a poor candidate for a lectotype. The left valve figured by Waring (1917, PI. 7, fig. 1; CAS 61644.02) is more complete and is designated here as the lectotype. The specimens CAS 61644.01 and CAS 61644.03 are designated as paralectotypes.
Propeamussium (Parvamussium) cowperi is known from four specimens. Two of these specimens are probably deformed. Specimen CAS 61644.01 and counterpart CAS 61644.05 have expansion cracks and may be flattened, and specimen CAS 61644.03 has structural lineations and may be tectonically elongated. As a result, the measured variables for these specimens are probably unreliable (although ratios of distances taken in the same axis are probably reliable (i.e., RH/H)), and valve outline of the species cannot be determined. In addition, some morphological features are not preserved or poorly preserved on the specimens, thus preventing a complete description of the species.»
SUNDBERG, F. A. 1989. Propeamussium Species (Bivalvia: Propeamussiidae) from the Upper Cretaceous of Southern California. Journal of Paleontology, 63 (1): 53-63, figs. 1-9. [p. 61]
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Propeamussium (Parvamussium) cowperi (Waring); F. A. Sundberg, 1989, Propeamussium Species (Bivalvia: Propeamussiidae) from the Upper Cretaceous of Southern California, figure 8.
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