Chlamys sespeensis hydei (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. 69, pl. 8, figs. 3, 3a, 3b]
«PECTEN (CHLAMYS) SESPEENSIS var. HYDEI n. var.
Pl. V, figs. 3, 3a, and 3b. 1903. Pecten ( Chlamys) hydei Arnold. MS.
Description.— Shell averaging about 45 millimeters in altitude, much higher than long, subequivalve, slightly convex, and subequilateral, except for ears; anterior sides more concave than posterior; base regularly rounded; umbonal angle comparatively small. Right valve with about 20 subequal, prominent, rounded, somewhat imbricated ribs, which increase gradually in number by division and intercalation as the shell grows; interspaces somewhat narrower than ribs and often containing one or two thread-like intercalaries; ears as in P. hastatus var. hericius except less imbricated, and the posterior relatively larger. Left valve similar in every respect to right.
Dimensions.— Alt. 46 mm.; long. 39 mm.; diameter 13 mm.; umbonal angle 82°. This variety is characterized by the nearly uniform size of its ribs and interspaces. The shell has a tendency to contract somewhat upon reaching an altitude of about 35 or 40 millimeters. P. var. hydei is closely allied to the typical P. sespeensis, but may usually be distinguished by its more nearly equal ribs, which are generally more strongly imbricated. In a tributary of Little Sespe Creek, Ventura County, Mr. Eldridge found P. var. hydei associated with Scutella fairbanksi, Ostrea sp., Arca sp., and Balanus. Near the Torrey wells, Ventura County, the same gentleman found it with Mytilus mathewsonii, and Ostrea (aff.) titan. In the Ojai Valley it occurs with Pecten magnolia and Chione n. sp. (large; coarse sculpture). The type specimen is from Lynch's Mountain, Monterey County, where it was found associated in the lower Miocene (Vaqueros sandstone) with Turritella hoffmanni, Pecten estrellanus, and other species characteristic of this horizon. It is now in the collection of Delos Arnold. Named in honor of Prof. James M. Hyde, of the University of Oregon. RANGE.
Miocene (lower). Lynch's Mountain, Monterey County (Arnold); vicinity of Little Sespe Creek, Torrey oil wells, and Ojai Valley, Ventura County (Eldridge).»
RALPH ARNOLD, 1906
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R. Arnold, 1906, plate 8.
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