Eburneopecten hamiltonense (Tucker-Rowland, 1934)
TUCKER-ROWLAND, H. I. 1934. Some Atlantic Coast Tertiary Pectinidae. The American Midland Naturalist, 15: 612-621, pls. 25-27 [Under H. I. Tucker] [p. 617, pl. 27, fig. 1]
1934 Amusium (Pseudamussium) hamiltonensis Tucker-Rowland, 1934
H. I. Tucker-Rowland, 1934,
plate 27. |
«Pecten (Chlamys) clarkeanus Aldrich, Dall, Wag. Free Inst. Sci., Trans. vol. 3, pI. 4, p. 739, partim, 1898.
Pecten clarkeanus Aldrich, Harris, Bull. Am. PaI., vol. 6, p. 25, partim, pl. 15, figs. 10, 11, 12, 1919. Description. — Shell somewhat thin; valves nearly equally convex and discrepantly sculptured. Right valve resembles scintillatus Conrad in outline. Beak pointed, faint radial striations best developed over the central portion of the disk; concentrically sculptured. Auricles subequal, the right has 4 radials, the left is plain. The left valve slightly more convex than the right; having the quinque-costate structure noted by Harris. Sculpture perhaps slightly stronger on this valve. Extending back: fcom the beak about 7 mm., the concentric and radial sculpture intersect, giving the shell a somewhat cancelllate appearance. Disk obscurely striated radially. Concentric sculpture rather stronger than on the right valve. Auricles subequal, the posterior auricle has 4 radials, the anterior none. At the point where the auricles are attached to the disk there is a row of close set, elevated, rounded scale-like processes which are evidently formed by the continuation of the concentric sculpture of the disk. This character seems to be present in none of the related species. The holotype shows only traces of obscure camptonectes striation on the submargins. Dimensions. — height, 21, width 19 mm.
Two young valves from Talahatchee, Miss. may belong to this species. They show cancellate sculpture over the entire disk and strong camptonectes marking. The larger left valve, height 9 mm., has five strong radials on the posterior auricle, three feeble ones near the submargin on the anterior. The posterior one has the canellate sculpture of the disk. Remarks. — This species is separated from scintillatus by its sculpture. That species is never radially sculptured, has much more strongly developed camptonectes sculpture, and never has the row of scales at the base of the auricles of the Ieft valve. It is separated from clarkeanus by its much less well developed radial sculpture. Some specimens of clarkeanus have the cancellate sculpture on the beaks of the left valves, but all such specimens examined show the fairly strong radial ribbing at the margin of rhe disk, sometimes also on the anterior and posterior slopes of the disk. Aldrich states in the description of clarkeanus that it combines the characters of two subgenera. Certainly the holotype of this species should be referred to Pseudamussium, while the strongly ribbed forms referred to clarkeanus are properly included under Chlamys.
Occurrence. — Claiborne Eocene. Hamilton Bluff, Ala. (type); Talahatchee, Miss.
Holotype. — A left valve. Collection PaIeontological Research Institution, Ithaca, New York .
Paratype. — A right valve from the type locality.
Dimensions: Height 20, width 16 mm. Collection Paleontological Research Institution, Ithaca, New York.»
HELEN IONE TUCKER-ROWLAND, 1934
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