444 A, E. Verrill—Mollusca of the New England Coast. 
Crenella fragilis Verrill, sp. nov. 
Shell large for the genus, very thin and fragile, translucent, irides- 
cent within, in form oblong-ovate, very oblique, the anterior end 
short, a little expanded and broadly rounded, while the shell is very 
much swollen and prolonged ventrally. The posterior side falls off 
rapidly from the beak and is only a little convex, so that the margin 
of the valve has a nearly elliptical outline, with the longer axis 
extending from the beak to the ventral margin. The umbos are 
prominent and the beaks are strongly incurved and turned forward, 
and separated from the margin of the shell by a deep, narrow 
ligamental groove. The hinge-margin is thin and nearly plain, with- 
out any denticles. The ligament is long and extends from the front 
of the beak back more than a third of the length of the posterior 
margin. The sculpture consists of very regular, fine, radiating, 
raised lines, scarcely visible without a lens, separated by furrows a 
little wider; these are more or less interrupted by numerous fine but 
irregular raised lines of growth. The epidermis is very thin, smooth, 
pale olive. 
Height of the smaller example, from beak to ventral margin, 14™"; 
length from anterior to posterior margins, 9""; thickness, 12". A 
broken specimen from the same locality is more than twice as large 
as the one measured, 
Station 2,265, off Chesapeake Bay, N. lat. 37° 07' 40”, W. long. 
74° 35’ 40”, in 70 fathoms, green mud, gravel, and broken shells; 
bottom temperature 63° F. Two dead but fresh specimens (Nos. 
40,676 and 41,543). 
This species is remarkable for its large size, compared with other 
species ; the extreme thinness and translucency of the shell; and for 
the fine and regular radiating lines that cover the entire surface. 
Pecten undatus Verrill and Smith, sp. nov. 
PLATE XLIV, FIGURE 21. 
Shell small, oblique, very thin, fragile and translucent. The valves 
are similar in form and sculpture, but the left is a little more convex. 
Both are regularly undulated and everywhere covered by numerous, 
rather fine and regular raised radiating lines. In the right valve the 
anterior ear is considerably prolonged; with a deep acute notch 
below it; in the other valve the ear is less elongated and the notch 
is shallow and broadly concave; the posterior ear in both valves is 
