Parvamussium diomedeum (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, 153: i-iv, 1-233, pls. 1-58. [p. 83, pl. 20, figs. 3, 4; pl. 21, figs. 1-4]
1938 Propeamussium diomedeum Dall, Bartsch & Rehder, 1938
W. H. Dall, P. Bartsch & H. A. Rehder, 1938, plates 20, 21
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«Shell inequivalved, the right considerably smaller and appressed to the inside of the left valve, alabastine, with the internal ribs shining through the substance of the shell as white streaks. The anterior and posterior wings of the right valve have no radiating ribs, but only fine obsolete concentric threads, which terminate at the dorsal margin in fine denticulations. The central disk of the right valve has no radiating sculpture, but only feeble. obsolete, closely spaced, concentric threads, which are separated by slender impressed lines. The left valve has the anterior wing considerably larger than the posterior, but here, too, there are no radiating ribs in either of the wings. The anterior wing has rather strong lamellae at its junction with the central part, which fade dorsally, while the posterior wing is almost smooth except for lines of growth. The central disk of the shell is marked by numerous, radiating threads and fine concentric lamellae which are best developed on the early half of the shell where they enclose squarish or slightly rectangular pits. The junction of the radiating and concentric sculpture produces slender nodules. The concentric threads are more closely approximated toward the ventral margin. The hinge area is very narrow. The inside of the shell bears 10 radiating ribs and three intercalated short pieces near the ventral margin between the second and third, third and fourth, and seventh and eighth, figuring from the anterior margin posteriorly.
The type, U.S.N.M. Cat. No. 190442, was dredged by the U. S. Bureau of Fisheries Steamer Albatross at Station 3883 in Pailolo Channel in 277-284 fathoms in globigerina ooze; bottom temperature 45.2° F. It measures: height. 6.5 mm.; length, 6.5 mm.; diameter, 2.2 mm.
This species is readily distinguished from the Hawaiian Propeamussiums with solid concentric lamellae on the left valve, by having no radiating sculpture on the wings.» WILLIAM HEALEY DALL, PAUL BARTSCH & HARALD ALFRED REHDER, 1938
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