Chlamys landesi (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. 3-5]
1906 Pecten (Chlamys) landesi Arnold, 1906
R. Arnold, 1906, plate 2.
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«Description.— Shell averaging about 34 millimeters in altitude, about as long as high, subcircular, inequivalve, equilateral, thin, slightly ventricose, and with serrate margins. Right valve more ventricose than left, and flattening toward the periphery in the adult; surface ornamented by from 25 to 40 subequal, rounded, more or less imbricate ribs, separated from each other by subequal, concave-bottomed interspaces, which average about as wide as the ribs; hinge line slightly longer than one-half length of disk; ears somewhat unequal, the anterior being slightly the longer; anterior ear sculptured by 4 prominent radials, while the posterior has from 6 to 8 less prominent ones; byssal notch deep; whole surface of disk and ears crossed by numerous fine imbricating lamellae. Left valve more compressed than rjght, similarly sculptured, but with both ears slightly obliquely truncated, the anterior one showing a broad shallow notch. Hinge and muscle scars similar to P. islandicus.
Dimensions.— Alt. 34 mm.; long. 33.5 mm.; hinge line 19 mm.; diameter 12 mm. (right valve 7 mm., left valve 5 mm. ). The general outline and convexity of all the shells of this species appear to be about the same, but the ribs are quite variable, as regards both number and shape. In most cases the ribs are evenly rounded and about equal in width to the interspaces, but in some cases they are ridgelike and narrower than the interspaces. In some specimens a few of the ribs become dichotomous distant 10 or 15 millimeters from the umbo, and small riblets are intercalated in a few of the interspaces at about the same distance. One specimen is contracted at a distance of about 30 millimeters, and shows several intercalaries beyond the line of contraction. Some of the specimens of P. landesi remind one somewhat of P. membranosus Morton, from the Eocene of North Carolina, although the latter has more and narrower ribs, and is ornamented by finer imbricating sculpture than the former. P. landesi is distinguishable from P. proavus by its relatively longer disk and fewer but more prominent, regular, and less imbricated ribs. It is distinguishable from P. calkinsi by its smaller size when adult, fewer but more elevated ribs, and relatively much shorter hinge line. P. landesi is found quite abundantly in a dark-greenish sandstone bed that outcrops about 100 yards west of the junction of Stillwater and Olequa creeks (U. S. Nat. Mus. locality 4019) one-fourth mile southwest of Little Falls, Lewis County, Wash. It is also found in a similar matrix in the bed of Olequa Creek (U. S. Nat. Mus. 4024), 1 mile north of the first locality. It is associated in this formation with a characteristic Eocene fauna, among which are the following species: Venericardia planicosta Lamarck, Thracia dilleri Dall, Crassatellites sp., Meretrix sp., Ostrea sp., Pteria (cf.) limula Conrad, Cardium 2 sp., Barbatia sp., Glycymeris sp., Corbula sp., Callista sp., Turritella (cf.) uvasana Conrad, Fusus 4 sp., Ocinebra sp., Ranella sp., Calyptrophorus sp., Lunatia sp., Turbinella (?) sp., Murex 2 sp., Conus sp., Cassis sp., Tritonium sp., Dentalium ( cf.) cooperi Gabb, and Nautilus sp. This horizon is probably upper Eocene, possibly above the Tejon. Named in honor of Prof. Henry Landes, Seattle, Wash. RANGE.
Eocene (probably upper). Vicinity of Little Falls, Lewis County, Wash. U. S. Nat. Mus. locality 4019; 4024. (Arnold.)»
RALPH ARNOLD, 1906
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