“CYAMIUM DENTICULATUM.
(Pl. III., figs. 4-4b.)
Shell small, rounded, rather convex, almost equilateral, rather thin, whitish,
covered with a very thin, glossy, yellowish periostracum, marked with very fine
striæ of growth and numerous shallow, narrow, and not very conspicuous radiating sulci or impressed lines. The latter are visible on the inner surface of the valves, which are finely denticulate at the margin; the muscular impressions are indistinct. Hinge composed of two diverging teeth in the right valve (fig. 4b, t.), and three in the left (figs. 4a, t.), the anterior in the right and the central one in the left beinmg somewhat bifid. The posterior lateral margin of both valves is produced into a pseudo-lateral tooth (figs. 4a, 4b, m.); the ligament (figs. 4a, 4b, l.) is oblique, posterior to the teeth, and mostly internal; but a slight portion is visible externally, when the valves are closed, just behind the tip of the umbones; the prodissoconch forms a circular, smooth, glossy, white, convex disc at the apex of each valve.
Length 4.3 millim.; height, 4; diam., 3.
Hole 3. In 12¾ fathoms, stones and gravel.
Although the general aspect of this species is very unlike that of the typw of the genus Cyamium, still the characters of the hinge appear to be so very similar that it does not seem to be advisable at present to separate them generically. “
(Smith, 1907: 3-4)
