Chlamys (Chlamys) beringiana unalaskae 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. 20, figs. 1, 3, 4]
«Chlamys (Chlamys) beringiana unalaskae MacNeil, n subsp.
Plate 20, figures 1, 3, 4 Description.— Shell of medium size and moderately inflated, right valve more inflated than left valve. Anterior ear of right valve moderately long and narrow, byssal notch moderately wide, moderately deep, and angulate. Anterior ear of left valve of moderate length and very broad, anterior margin weakly sinuous; posterior ear short, steeply sloping margin. Anterior dorsal margin longer and more concave than posterior margin. Dorsal slopes of moderate width and very slightly undercut. Ribs, particularly of the left valve, gently curving toward the anterior with growth. Right valve with broad, flat-topped fascicles and narrower, shallow, rounded interspaces; both fascicles and interspaces with moderately strong riblets that are more or less evenly spaced. Left valve with moderately strong fascicles and wider interspaces, both the facicles and interspaces with strong riblets, usually with two to four riblets forming the crest of the fascicles. The riblets extend without convergence to the juvenile stage; a few are added interstitially in the adult stage. The riblets of both valves have small closely set scales or beads. The microsculpture of the juvenile stage is usually reticulate or metal lathelike, but in adults the surface between the riblets is usually either smooth, marked by concentric growth lines, or bears very fine radial lines.
The left valve shown on plate 20, figure 3, has no reticulate sculpture in the juvenile stage. An unfigured fragment of a left valve has reticulate microsculpture on both ribs and interspaces, well into the adult stage. Discussion.-- This is another of the peculiar forms that appears, on the basis of existing records, to be restricted to waters immediately surrounding Unalaska. This form is made a subspecies of C. beringiana because of its longer anterior dorsal margin and because of the similarity of the right valve to right valves of typical C. beringiana, from the Pribiloffs (pl. 21, figs. 2, 7). Pending further knowledge of this subspecies, it might with equal justification be combined with C. islandica albida. C. islandica powersi has its reticulate microscultpture restricted to the juvenile stage, but a left valve of C. beringiana subsp.? from Point Hope (pl. 20, fig. 2) has reticulate microsculpture over the entire shell except for the narrow crest of a few ribs. The left valve of C. b. unalaskae is bright orange and the right valve is yellowish with several concentric orange bands. Specimens of C. beringiana from the Pribiloffs are mostly orange with narrow purple bands, and specimens from Saint Lawrence Island are mostly purple with orange bands. Specimens from Point Hope and Point Barrow are purple. There seems to be a color gradation in this species, therefore, from south to north. Grau (1959, p. 73) stated that C. islandica albida, the only living Alaskan form with which C. b. unalaskae might be confused, is white or very pale pink. I can find no figures or descriptions of an Alaskan shell that could be this subspecies, and the type lot of 10 whole and incomplete specimens may be the only ones ever found. It is undoubtedly a very rare pectinid. Types: The holotype (USNM 637751), a right valve, measures 55 mm in height and 42 mm in length. Two paratypes (USNM 637752, 637753) are both left valves. Type locality: Recent, Usof Bay, southeastern Unalaska Island, Aleutian Islands, Alaska, USGS D53. Picked up on the tidal flat.» FRANCIS STEARNS MACNEIL, 1967
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F. S. MacNeil, 1967, plate 20.
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