Cyclopecten lompicoensis (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. 89, pl. 23, fig. 5; pl. 27, fig. 8]
1906 Pecten (Pseudamusium) [sic] lompicoensis Arnold, 1906
R. Arnold, 1906, plates 23, 27.
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«Description.— Adult shell averaging about 11 millimeters in altitude, subcircular, inequivalve, thin, compressed; margins smooth. Right valve ornamented externally by numerous sharp, elevated, equal, equidistant, imbricating, concentric lamellae; hinge line equal to one-half length of disk; ears unequal; anterior nearly twice as long as the posterior, arcuately truncated and sculptured by regular, sharp, imbricating, concentric lamellae and 6 or 7 faint radials; posterior ear short, somewhat obliquely truncated and sculptured by concentric lamellae; byssal notch only faintly indicated. Left valve sculptured by concentric lamellae similar to those of the right, and, in addition, having numerous fine radiating strire, which usually become obsolete near the periphery in the adult shell; ears similar to those of the right valve, except that in the specimens examined no radials were noted on the anterior one. Hinge similar to that of P. randolphi.
Dimensions (of slightly distorted specimen).— Alt. 11.5 mm.; long. 11 mm.; hinge line 5. 5 mm. This beautiful little Pecten is allied to P. peckhami, but is distinguishable from the latter by its much more prominent and regular concentric lamellae, and by its well-defined ears, the anterior one of which on the right valve is relatively much shorter and broader than the analogous one in P. peckhami. The byssal notch in P. lompicoensis is also only faintly indicated, while in P. peckhami the notch is profoundly developed. P. lompicoensis is known only from the Miocene (exact horizon doubtful) shales at the head of Lompico Creek, Santa Cruz County, where it is associated with a Phacoides resembling acutilineatus Conrad. RANGE
Miocene. Head of Lompico Creek, Santa Cruz County (Newsom, Arnold).»
RALPH ARNOLD, 1906
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«Comments.— The right posterior auricle of C. lompicoensis is delineated, excluding it from Delectopecten, and no trace of internal ribs can be seen, excluding it from Propeamussium and Parvamussium. The only sculpture preserved is strong, almost equally spaced, concentric ridges on the right valve. The left posterior auricle seems not to be delineated.
I am indebted to T. R. Waller (written commun., 1979) who examined the holotype of this species and said that it "is definitely a member of the Propeamussiidae as evidenced by the presence of a prismatic structure over the entire right valve and lack of a ctenolium. I think that it can best be placed in Cyclopecten for the present." Geographic range.— Middle California. Geologic range.— Miocene Occurrence in California.— Monterey 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. B8]
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Cyclopecten lompicoensis (Arnold); E. J. Moore, 1984, Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae, plate 1, figure 2.
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