Chlamys hanaishiensis amchitkana MacNeil, 1967
MACNEIL, F. S. 1967. Cenozoic pectinids of Alaska,
Iceland, and other nothern regions. United States Geological Survey
Professional Paper, 553: iv, 57 p., pls. 1-25. [p. 30, pl. 12, figs. 3, 5; pl. 13, fig. 8; pl. 14, figs. 1-2, 4, 5 ; pl. 15, fig. 4; pl. 22, fig. 6]
1967 Chlamys (Chlamys) hanaishiensis amchitkana MacNeil, 1967
F. S. MacNeil, 1967, plate 12.
F. S. MacNeil, 1967, plate 13.
F. S. MacNeil, 1967, plate 14.
F. S. MacNeil, 1967, plate 15.
F. S. MacNeil, 1967, plate 22.
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«Pecten (Chlamys) islandicus, Stewart and MacNeil in Powers Coats, and Nelson, 1960, U.S. Geol. Survey Bull. 1028-P, p. 543.
Description.— This subspecies ranges from forms in which the ribs of the right valve remain undivided throughout the life of the individual to forms in which the ribs divide at an early age. Left valves of the former type have ribs of nearly uniform size; left valves of the latter type have single, moderately strong interstitial riblets between the main ribs. Discussion.— The variants with divided ribs and interstitial riblets are very closely related to C. rubida jordani (pl. 22, fig. 3; Woodring and others, 1946, pl. 32, fig. 16, as C. islandicus jordani). Typical C. r. jordani probably is a migrant of some part of this stock to southern waters. C. h. amchitkana grew to a much larger size than any known specimen of C. r. jordani. This form resembles C. pseudislandica plafkeri except for a greater tendency for the ribs to split and a greater tendency for the ribs of the left valve to be of equal size. C. h. amchitkana may prove to be no more than a variant of C. p. plafkeri, but the prevalence of this form on Amchitka and C. p. plafkeri on Middleton suggests there may be a geographical sorting as well. Two different collections of pectinids have been made from Pleistocene deposits at the head of South Bight, Amchitka Island. While no stratigraphic distinction has been made, the fossils suggest that more than one stage of the Pleistocene is represented. The collection containing C. h. amchitkana yielded Foraminifera that Cushman and Todd (in Powers and others, 1960, p. 543) compared with the fauna of the Timms Point Silt (early Pleistocene) of California. The pectinids in this collection are leached and chalky. Another collection of fossils contains different pectinids, C. coatsi, C. coatsi middletonensis, and C. islandica powersi. The shells in this collection are comparatively fresh, and some specimens are brightly colored. While the bay head fill has small areal extent, more than one period of fill is likely. Types: The holotype (USNM 644991), an incomplete right valve, measures 93 mm in height and 88 mm in length. Other figured specimens are numbered USNM 014992-644999. Type locality: Poorly bedded loose sand and gravel forming a fill about 75 ft thick at the head of South Bight, Amchitka Island, Aleutian Islands, Alaska, USGS 16908. Other occurrences: Middleton Island, USGS 17743, 17744.» FRANCIS STEARNS MACNEIL, 1967
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