Page:American Seashells (1954).djvu/125

Rh ally with a black-spotted edge and with a thickened central callus which is light-brown to black. A. albicosta C. B. Adams and A. fungoides Roding are the same. Moderately common in the West Indies, occasionally found on the Lower Florida Keys.

Small, flattish, uncoiled shells which are “hat-shaped,” similar to Acmaea, but the embryonic nucleus is spiral-the animal has no external gills and the proboscis is produced into a labial process on each s1de. The radula has a median tooth, which in Acmaea is absent.

$1/4$ to $1/2$ inch in maximum diameter, moderately conic, with straight sides, oval-elongate in outline. Rather fragile, dull-white to brownish externally and with ﬁne, granulose, crowded, radial threads. Interior white or tinged with pink. Apex usually eroded. A common cold-water species often dredged in shallow water off New England.

$1/4$ to $3/8$ inch in length, a little wider, with 5 evenly and well-rounded whorls. Narrowly and deeply umbilicate. Angle of spire about 90 degrees. Next to last whorl with 10 to 12 smoothish, raised, spiral threads. Columella and outer lip thin, sharp, the latter ﬁnely crenulate. Color rosy to grayish cream. White within the smoothish umbilicus. Aperture pearly-rose. Commonly dredged from IO to 62 fathoms. M. groenlandicus Möller is the same. Formerly known as M. cinereus Couthouy.