222 A. FE. Verrill—Mollusca of the New England Coast. 
what excavated, rather indistinctly defined by feeble undulations. 
The anterior end is short, very obtusely rounded or subtruncate ; the 
ventral margin is broadly rounded, slightly obliquely produced a 
little behind the middle, forming there a scarcely distinct, rounded 
angle, from which a posterior, ill defined, rounded ridge runs up to 
the beak; posterior end very obtusely rounded and ‘somewhat 
oblique; posterior dorsal margin descending rapidly from the beak 
and slightly convex. Surface nearly smooth to the naked eye and 
covered with a very thin, pale yellowish epidermis; under a lens the 
whole surface, except on the umbos, is covered with very slight, 
rather distinct radiating lines of very minute pointed granules, which 
are pretty evenly spaced along the lines, rather distantly on the 
middle area of the shell, but becoming much more numerous toward 
the posterior end, where they are connected by distinct but very fine 
raised lines, which appear to be chiefly epidermal; one line, more 
distinct and more elevated than the rest, runs from behind the beak 
to the upper part of the posterior margin, defining a narrow posterior 
dorsal area. The minute granules scattered over the surface appear 
to be chiefly due to the epidermis, but where the surface is somewhat 
rubbed they still appear as minute specks, which become very fine 
and irregularly scattered on the umbos; where most perfect, each 
granule is surmounted by a minute sharp process of the epidermis. 
The margin is sharp and plain, with a thickened interior ridge a’ 
short distance within the edge. The hinge consists of a large, stout, 
obtuse tooth, just below the beak, which projects considerably in- 
ward and is divided at the summit into three low, rounded lobes or 
cusps, of which the most interior is the largest and most prominent, 
while the outermost is confluent with the lunular margin ; a support- 
ing ridge runs from the inner margin of the tooth both forward and 
backward to the margins; posteriorly, between this ridge and the 
margin, there isa very narrow and long, curved ligamental groove, 
running forward and terminating just under the beak above the 
center of the large tooth ; a small, divergent, somewhat raised’ ridge- 
like process, grooved on top, intervenes between the anterior part of 
the ligamental furrow and the principal tooth. The inner surface of 
the shell is opaque white, and marked with slight irregular lines and 
grooves and with feeble undulations parallel with the lines of growth. 
Externally the shell is white beneath the thin, pale yellow epidermis. 
Length, 13°5™"; transverse breadth, 6"; height, from apex to 
ventral margin, 14°6™™. 
Station 2097, N. lat. 37° 56’ 20”, W. long. 70° 57’ 30", in 1917 
fathoms (No. 35,263), one dead but fresh specimen. 
