Lyriochlamys traskii (Gabb, 1864)
GABB, W. M. 1864. Paleontology of California. Volume I. Description of the Cretaceous fossils. Geological Survey of California. Paleontology Vol. I, Section IV: 57-217, pls. 9-32. [p. 200, pl. 26, figs. 187, 187a]
1864 Pecten traskii Gabb, 1864
W. M. Gabb, 1864, plate 26.
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«SHELL compressed, elongate, outline of the lower half forming two-thirds of a circle; margins of the body, above the curve, rapidly converging and straight. Right valve, anterior auricle long, truncated at the end, deeply excavated below; posterior auricle broad and obliquely truncated. Surface marked by numerous, radiating, squamose ribs, with sometimes smaller intermediate ones; the interspaces are marked by oblique lines, producing, under a glass, a woven appearance. These lines are represented too numerously in the figure 187 a.
Figure 187, natural size.
Locality: Texas Flat, Placer County (Division A.); collection of the California Academy of Natural Sciences; presented by Dr. Trask, after whom the species is named. The species seems to be rare, as there are remains of but two valves in the collection. One is very young; the other consists of the internal cast and its corresponding mould, the substance of the shell having decomposed. The drawing is from a wax cast of this mould.» WILLIAM MORE GABB, 1864
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«Lyriochlamys traskii is a moderately common component of the oyster-rich interval and also has been found at one locality in the massive sandstone facies. It is represented by numerous partial internal and external molds. This moderately large pectinid (up to 90 mm in height and 70 mm in width) is characterized by numerous radiating squamous ribs and occasional interribs extending to the margins of the disc and onto the auricles and by Camptonectes-like divaricate striae between the ribs. Growth lamellae may be prominent on large specimens, forming squamae at their intersections with the radial ribs. The degree of ornamentation and the roundness of the disc are quite variable (see Gabb (1864, 1869) for additional description).
This species has been listed from as far south as San Diego (Cooper, 1894) and the Santa Ana Mountains (Sundberg, 1980) to as far north as the Vancouver Island area (Whiteaves, 1903), as well as at several localities in the Sacramento Valley (Gabb, 1864; Stanton, 1893). It generally is associated with faunas indicative of Campanian to early Maastrichtian age but may be present in mid-Cretaceous strata of the Hornbrook Formation of northern California (Anderson, 1902). Lyriochlamys traskii is typically a rare faunal element where it has been found. The deep byssal notch developed on the right valve of this species indicates strong byssal attachment, probably to a hard substrate. The squamose ribs suggest that it has adapted to a fissure-dwelling lifestyle, as many bivalves having a Chlamys-like morphology have done (Kauffman, 1969), although the generally undeformed morphology of the specimens suggests growth in an unconfined habitat.» ELDER, W. P. 1991. Lyriochlamys traskii. An unusual late Cretaceous fauna from an Oyster-rich interval in the Santa Cruz Mountains of California. Shorter Contributions to Paleontology and Stratigraphy, United States Geological Survey Bulletin, 1934 E: 1-18, pls. 1-5. [p. 10]
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Lyriochlamys traskii (Gabb), 1864; W. P. Elder, 1991, An unusual late Cretaceous fauna from an Oyster-rich interval in the Santa Cruz Mountains of California, plate 1, figures 4, 6, 8; plate 2, figures 5, 8-10.
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