Swiftopecten hamlini (Arnold, 1906)
ARNOLD, R. 1906. The Tertiary and Quaternary pectens of California. United States Geological Survey Professional Paper, 47: 1-264, pls. 1-53. [p. 67, pl. 11, fig. 2]
1906 Pecten (Chlamys) hamlini Arnold, 1906
R. Arnold, 1906, plate 11.
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«Description.—Type somewhat distorted but originally about (60 millimeters in altitude, and probably somewhat shorter than high; moderately convex; base evenly rounded; sides nearly straight. Right valve with 4 broad, squarish ribs, each ornamented above by about 5 prominent imbricated radiating ridges, and separated by relatively narrow interspaces; hinge line more than one-half length of disk; anterior ear much longer than posterior and ornamented by several imbricated radiating ridges; byssal notch quite prominent; posterior ear short and radially ridged.
Dimensions.— (Of the distorted type.) Alt. 60 mm.; long. 68 mm.; hinge line 40 mm.; diameter 24 mm. This species is closely allied to P. wattsi but is distinguisiiable from the latter species by its relatively broader (?) disk and longer hinge line. The characteristics of sculpture are approximately the same in the two species. The geologic position of P. hamlini is somewhat uncertain, although the meager fauna with which it is associated at the type locality points toward its correlation with the Vaqueros or lower Miocene. The type of P. hamlini (U.S.N.M. No. 164S44) was collected by Mr. Homer Hamlin near the head of Slack's Canyon, in the Mount Diablo Kange, Monterey County, where it was associated with P. estrellanus Conrad, Chione n. sp. (large, and with coarse sculpture), Chione (cf.) mathewsonii Gabb, and Mactra (aff.) catilliformis Conrad. A specimen, which is probably a left valve of P. hamlini was found associated with Pecten branneri in the lower Miocene at Tuff Hill, near Stanford University, Santa Clara County. This specimen has three widely separated, narrow, ridge-like ribs, and the interspaces are ornamented by a number of rather coarse radiating riblets; altitude 31 millimeters. RANGE
Miocene (lower?). Locality 3851, U. S. Nat. Mus. , head of Slacks Canyon, Mount Diablo Range, Monterey County (Hamlin); Stanford University (Tuff Hill), Santa Clara County (Arnold).»
RALPH ARNOLD, 1903
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Comparison.— "This species is closely allied to P. wattsi, but is distinguishable from the latter species by its relatively broader (?) disk and longer hinge line. The characteristics of sculpture are approximately the same in the two species." (Arnold, 1906, p. 67)
"The original specimen of this species is very poor and badly distorted. Specimens in the collection at Stanford University show that it is a form of the P. swiftii type, distinguishable from the variety parmeleei of that species not by its shape but by its fewer, coarser secondary ribs." (Grant and Gale, 1931, p. 171) Comments.-- Judith T. Smith (oral commun., 1979) examined the holotype and felt that this species could be a distorted Lyropecten. Geographic range.— Middle California. Geologic range.-- Miocene (?). Occurrence in California.— Santa Margarita (?) Formation (Keen and Bentson, 1944). 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. B60]
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Swiftopecten? hamlini (Arnold); E, J. Moore, 1984, Tertiary Marine Pelecypods of California, plate 25, figure 5.
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