Similipecten nanus (Verrill & Bush in Verrill, 1897)
VERRILL, A. E. 1897. A study of the family Pectinidae, with a revision of the genera and subgenera. Transactions of the Connecticut Academy of Arts and Sciences, 10: 41-95, pls. 16-21. [p. 85, pl. 16, figs. 12, 12a-12c (as parvus)]
1897 Cyclopecten nanus Verrill & Bush in Verrill, 1897
A. E. Verril, 1987, plate 16.
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«Shell small, the breadth and height about equal; the valves are nearly equal in size and convexity. Dorsal hinge-margin rather long and straight; auricles relatively large and broad, both ends subtruncated or a little convex in the left valve, and forming nearly a right angle with the dorsal margin; anteriorly not well differentiated from the body of the shell. In the right valve the anterior auricle is narrow and somewhat more elongated and obtusely rounded at the end, with a sharp, angular, byssal notch beneath it and separated from the body of the shell by a narrow groove.
The dorsal margins of the body of the shell are nearly straight and form rather more than a right angle. Ventral margin broadly rounded, nearly semi-circular, forming a very obtusely rounded angle where it joins the dorsal margins. Umbos a little prominent, with a small, smooth, rather acute, incurved beak, which usually projects a little above the hinge-margin. The surface of the left valve is everywhere thickly covered with fine, almost microscopic, radiating striae, which become a little more distinct on the anterior auricle; on some parts of the shell very thin, slightly raised, concentric lamellae or lines of growth are often distinct, especially on the anterior auricle, where they become closer and more regular; in crossing the radial striations they produce a microscopic decussation, which is often quite regular. The sculpture on the posterior auricle, though finer, is similar, but in many specimens the surface is nearly smooth or marked only by very fine radial striae. The body of the shell of the right valve is smooth, except for very fine concentric lines; on the anterior auricle are three to six or more distinct radial ridges, which are roughened by conspicuous lines of growth; the margin below the byssal notch is entire; the posterior auricle is nearly smooth. The internal hinge-plate is thin in the middle, but relatively broad on each auricle, and is crossed by numerous fine, well marked, transverse incisions; these are much more conspicuous than in most of the related species, whether young or old. The resilial pit is small, rounded, and situated just under the beak. There are no internal lirae. The inner surface is smooth and glossy, although in fresh specimens the external radiating lines show through by translucency. The ground-color of the right valve is yellowish or grayish white, with more or less numerous light yellowish brown, or reddish brown spots and blotches, and sometimes with irregular patches of opaque white; right valve white, sometimes with a few yellowish-brown spots. Some specimens are nearly destitute of spots. The right valve is less convex than the left, and its ventral edge does not quite reach that of the opposite valve; the umbo is less prominent; the beak is less acute and scarcely projects beyond, and often falls short of the hinge-margin, but the inequality is less marked than in most of the allied species. Length of one of the largest specimens 7 mm; height 6 mm; dorsal hinge-margin 4mm. It was taken in considerable numbers. It is so distinct from all the other species of our coast that a detailed comparison is unnecessary. Off the eastern coast of the U. States, opposite Chesapeake Bay and Cape Hatteras, in 43 to 132 fathoms. Although very small, this species seems to be adult.» ADDISON EMERY VERRILL & KATHARINE JEANETTE BUSH, 1897
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