Chlamys wainwrightensis MacNeil, 1967
MACNEIL, F. S. 1967. Cenozoic pectinids of Alaska, Iceland, and other nothern regions. United States Geological Survey Professional Paper, 553: iv + 1-57, pls. 1-25. [p. 27, pl. 18, fig. 3; pl. 19, figs. 8-9; pl. 23, figs. 4, 5]
«Chlamys (Chlamys) wainwrightensis MacNeil, n. sp.
Plate 18, figure 3; plate 19, figure 8, 9; plate 23, figures 4, 5 Description.— This species has a very inflated left valve and a very weakly inflated right valve. Shell relatively high for its width. Dorsal margins of unequal length with the anterior margin longer than the posterior margin, making shell slightly asymetrical. Dorsal slopes of right valve narrow, but those of the left valve broad, concave, and weakly undercut. Ribs of right valve low and rounded, straight sided; occasional ribs are split, evenly or unevenly. The interspaces are gently rounded, and some interspaces have a
small interstitial riblet. The left valve has higher and sharper ribs than the right valve; on some individuals nearly all ribs are split; other individuals have only one or two split ribs. Some individuals have a very weak tendency for the ribs to be differentiated into primary, secondary, and tertiary series. The interspaces are well rounded and usually roughened by growth lines. The microsculpture is reticulate or metal lathlike and covers most of the interspaces; it may or may not be present on the ribs. Right valves of living specimens have alternating broad orange and white bands, sometimes with a purple narrower band above the orange band; left valves are almost uniformly dark reddish purple. Discussion.— This species is recognized with certainty only along the coast of Chukchi Sea between Point Hope and Wainwright, Alaska. Its closest known relative is a form from the Okhotsk Sea that Kotaka (1962, pl. 34, figs. 18-23) referred to C. islandica erythrocomata. C. wainwrightensis resembles C. beringiana by having an elongate anterior dorsal margin, but it differs from C. beringiana and its subspecies by being less inflated; the right valve is very weakly inflated. A large suite of specimens of C. rubida hindsii from Excursion Inlet, southeastern Alaska, shows a gradation form individuals with more typical inflated equilateral right valves to individuals with abnormally flat right valves and longer anterior dorsal margins. None of the left valves in this suite, however, have the ribs divided into primary, secondary, and tertiary series as in C. wainwrightensis. There is some resemblance between C. wainwrightensis and C. tjornesensis (pl. 25, figs. 1-3) from supposed late Pliocene beds of Iceland. The left valves also recall left valves of the Pliocene forms here referred to C. cf. C. hanaishiensis (pl. 9, fig. 4) and C. chaixensis (pl. 9, fig. 2). The exact relationship between all these forms is at present unknown, nor is it clear whether they originated in the Pacific Ocean or in the Atlantic Ocean. As was stated previously, stocks of European early Tertiary origin might have reached the northern Pacific by either an Arctic or a Tethyan route. Types: The holotype (USNM 637756), a left valve, measures 69 mm in height anl 61 mm in length. The para type (USNM 637757) is a right valve from the same locality. Other figured specimens are numbered USNM 637754-637755, 637758. Type locality: Recent, Point Hope, Alaska, USGS M1339. Other occurrences: Recent, Wainwright, Alaska, USGS M2056, M2062, D318.» FRANCIS STEARNS MACNEIL, 1967
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F. S. MacNeil, 1967,
plates 18, 19, 23. |