Chlamys calkinsi (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. 51, pl. 2, figs. 1, 2]
1906 Pecten (Chlamys) calkinsi Arnold, 1906
R. Arnold, 1906, plate 2.
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«Description.— Shell averaging about 35 millimeters in altitude, subcircular, equivalve or nearly so, equilateral, rather thin, somewhat ventricose, and with only slightly serrate margins. Right valve with the exterior surface ornamented by about 55 small, squarish, slightly imbricated ribs, which show a tendency to become dichotomous near the end in some specimens; interspaces channeled and about one-half as wide as the ribs; hinge line about three-fifths the length of the disk; ears equal in length, flat and with the swell of the disk commencing at right angles to them; anterior ear sculptured by 4 or 5 imbricated radiating ridges; byssal notch distinct; posterior ear sculptured in a similar manner to the anterior. Left valve similar to the right except that in the former the ribs are slightly more rounded and the anterior ear has no notch.
Dimensions.— Alt. 30 mm.; long. 31 mm.; hinge line 18 mm.; diameter 6 mm. So far as known this species has no closely allied forms in any of the other California Tertiary formations, and for that reason is admirable as a diagnostic form for the Tejon. The type and several other specimens of this species were among some material collected by Dr. H. W. Fairbanks on the north side of the Sisar Valley, north of the Astarte oil wells, Ventura County. At this locality it was associated with the following characteristic Tejon fauna: Arca sp., Cardium breweri, Meretrix horni, Modiolus ornatus, Tapes sp., Turritella uvasana, Venericardia planicosta Lam. var. hornii. The types of P. calkinsi are now in the collection of the University of California. Named in honor of Mr. Frank C. Calkins, of the United States Geological Survey. RANGE.
Eocene (Tejon). Sisar Valley, Ventura County (Fairbanks).»
RALPH ARNOLD, 1906
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