Parvamussium molokaium (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. 82, pl. 20, fig. 8; pl. 21, figs. 5, 6]
1938 Propeamussium molokaium Dall, Bartsch & Rehder, 1938
W. H. Dall, P. Bartsch & H. A. Rehder, 1938, plates 20, 21.
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«Shell very small, milk-white, with the internal ribs showing through the texture of the shell. A narrow byssal notch is present at the junction of the anterior wing in the right valve with the median portion of the shell. Dorsal to this, this wing is marked by nine slender radiating threads and a tumid area at the dorsal border. The wing is also marked by numerous, closely spaced, concentric, slender lamellae which give the dorsal edge a scaly appearance. The posterior wing is smaller than the anterior and is marked by rather prominent and rather distantly spaced lamellae, between which finer lamellae are present. The dorsal border here, too, is scaly. The central disk is marked by numerous slender concentric lamellae which wear into rounded cords on the early part of the shell, but toward the ventral margin are still borne as thin shelves sloping ventrally. Here, too, they are very closely crowded. A part of the hinge being fractured, we are only able to say of the interior that the dorsal margin is denticulated, the narrow ligamental area finely transversely striated and that the central portion bears 17 radiating ribs. The left valve of this species is not known.
The type, U.S.N.M. Cat. No. 335677, was dredged by the U. S. Bureau of Fisheries Steamer Albatross at Station 3837 off the south coast of Molokai in 13 fathoms on yellow sand bottom; surface temperature 76° F. It measures; height, 7.2 mm.; length, 7.4 mm.; diameter of the single valve, 1.5 mm.
This species can at once be distinguished from its nearest Hawaiian relative, Propeamussium pailoloum by its much larger number of internal ribs.» WILLIAM HEALEY DALL, PAUL BARTSCH & HARALD ALFRED REHDER, 1938
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