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TROCHIDAE 107
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.
Fajnily LEPETIDAE
Genus Lepeta Gray 1842
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 side. The radula has a
median tooth, which in Acmaea is absent.
Lepeta caeca Miiller Northern Blind Limpet
Arctic Seas to Cape Cod, Massachusetts.
Plate 17J
Va: to Y2 inch in maximum diameter, moderately conic, with straight
sides, oval-elongate in outline. Rather fragile, dull-white to brownish exter-
nally 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.
Superbamily TROCHACEA
Faiitily TROCHIDAE (Top Shells)
Subfaimly MARGARITINAE
Genus Margarites Gray 1847
Subgenus Margarites s. str.
Margarites costalts Gould Northern Rosy Margarite
Plate lyt
Greenland to Cape Cod, Massachusetts. Bering Strait to Port Etches,
Alaska.
% to % 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 i o 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 lo to 62 fathoms. M. groenlandiciis Moller is the same.
Formerly known as M. cinereus Couthouy.