Pecten diomedeus Dall, Bartsch & Rehder, 1938
DALL, W. H., P. BARTSCH & H. A. REHDER. 1938. A manual of the Recent and fossil marine pelecypod mollusks of the Hawaiian Islands. Bernice P. Bishop Museum Bulletin, Honolulu, 153: i-iv, 1-233 pls. 1-58. [p. 96, pl. 24, figs. 7-8]
1938 Pecten diomedeus Dall, Bartsch & Rehder, 1938
W. H. Dall, P. Bartsch & H. A. Rehder, 1938, plate 24.
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«Shell rather large, the upper valve slightly cupped, pale brown, with the right wing markecl by incremental, closely spaced, lamellae only, and the left wing with a few decidedly obsolete threads near its dorsal border, which are too ill defined to be counted. This wing is also markecl by closely spacecl concentric lamellae. Both wings are clecicledly concave; the right wing is slightly curved and the left wing strongly so at its lateral margin. The central portion of the disk has its anterior and posterior border strongly rounded. The posterior rounded portion is marked by 7 obsolete radiating threads, of which the inner two are in pairs and smaller than the rest. The anterior rounded portion shows two very feeble, broad, rounded threads near its inner margin.The resi of the disk is marked by 11 broad, low, rounded, strong, radiating ribs, which show a tendency toward median grooving. The entire disk is marked by rather closely spaced, concentric lamellae. The ventral border of the shell is rendered slightly fluted by the ribs. The inside of the shell is porcelaneous. The dorsal edge of the hinge is almost straight. The resilial pit is broadly triangular. There are four oblique folds on the anterlor portion of the hinge, of which the second is much broader than the rest. On the anterior portion the folds are too badly worn to permit of proper description. On the anterior part the folds and threads show the closely spacecl, lamellar, vertical sculpture. The central disk of the interior shows strong grooves separated by flattened spaces corresponding to the external ribs and grooves in reversed order. The muscle scar is only feebly outlined.
The unique type, U.S.N.M Cat. No. 355570, is an upper valve dredged by the U. S. Bureau of Fisheries Steamer Albatross at Station 3855 off the south coast of Molokai in 130-127 fathoms on fine broken shell and coral bottom; bottom temperature 65.5º F. It measures: height, 53.5 mm.; length, 59.5 mm.; diameter of single valve, 7.5 mm. This species differs from Pecten waikikius in having the upper valve much less strongly cupped and in the absence of the radiating threads on the wings. The concentric sculpture also is regularly much finer.» WILLIAM HEALEY DALL, PAUL BARTSCH & HARALD ALFRED REHDER, 1938
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«This species is still known only from the type, a left valve differing from those of waikikius in being much less concave, and in its lack of auricular radial threads, in its ill-defined muscle scar, and in its lower ribs.
Examination of the holotype confirmed the impression that led to classification under benedictus (Fleming, 1957), and the uniformity of the waikikius sample now available strengthens the case for its specific distinction. This will not be certain, however, until right valves are obtained, since left valve concavity (and thus probably the nature of the adductor scar) are known to vary markedly in some Pecten populations (cf Fleming, 1957: 47) and auricular ribs are obsolete in some specimens of waikikius.» FLEMING, C. A. 1962. On the hawaiian scallops of the genus Pecten Muller (Pelecypoda). Pacific Science, 16: 181-185, fig. 1. [p. 184]
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