A, E. Verrill— Mollusca of the New England Coast. 223 
This species is very distinct from P. granulata and P. rotundata 
Jeff., both in form and in the character of the surface, which in both 
the latter forms is covered with comparatively large, rounded 
granules or small pustules, often closely crowded together, while in 
this species the granules are almost microscopic in size and separated 
by comparatively wide intervals, or they even appear remotely 
‘scattered on some parts, so that the shell presents a nearly smooth 
appearance to the naked eye, or when moderately magnified, which 
is strongly in contrast with both the other described forms. ‘The 
form of the shell in this species is also much shorter and more tumid, 
with higher umbos and more prominent beaks. The character of the 
hinge, however, agrees pretty closely with that of P. granwlata, but 
the tooth is larger and stronger. 
Nezra undata Verrill, sp. nov. 
A large species remarkable for its short broad form, its abbreviated 
siphon and the undulated character of the surface. Shell broad-ovate, 
not much swollen, with the beaks not far from the middle. The pos- 
terior dorsal margin descends rapidly in a nearly straight line; the 
posterior end is broadly, obtusely truncated and only slightly pro- 
longed; the ventral margin is very broadly curved ; the posterior 
margin less broadly rounded. The surface, especially anteriorly, is 
covered with undulations formed by narrow, raised, subtriangular 
ridges separated by rather wide, shallow, concave intervals, much as 
in most species of Astarte. These fade out, more or less, posteriorly 
and toward the ventral margin, where they are replaced by regular, 
concentric, raised lines. Hinge-margin of the right valve moderately 
thick. The cartilage-pit is not very large, descending, directed 
obliquely backward. Posterior lateral tooth is not very prominent, 
having the form of an elongated, thickened ridge, its most promi- 
nent point only a short distance back of the cartilage. 
Length, 24™™; height, 18™™; thickness, 13™™. 
Station 2098, off Chesapeake Bay, in 2221 fathoms. A single 
valve, considerably broken, (No. 35,256). 
Nezra gigantea Verrill, sp. nov. 
Shell very large, thick and opaque, short, stout, with prominent 
umbos, and short, wide beak, with the muscular scars and pallial lines 
deeply sunken. The shell is swollen and broadly rounded in front, 
with the ventral edge broadly rounded, narrowing gradually to the 
