MUSEUM OF COMPARATIVE ZOOLOGY. 231 
Lucina Blakeana, sp. nov. 
Plate II. Figs. 16, 17. 
One living specimen was found at Station 326, off Cape Fear, N. C., in 464 
fathoms. 
Shell of moderate size, a little longer than high, moderately convex, with a - 
well-marked posterior undulation, rather thin, translucent white under a con- 
spicuous light yellow epidermis. Umbos white, central, prominent, smooth 
near the beaks, which are small, pointed, curved strongly forward. Lunule 
long, rather broad, lanceolate, smooth, well excavated, so that the anterior dor- 
sal margin is straight and slopes obliquely from the beaks. From this the 
margin rises slightly, curves well forward, forming a prominent, well-rounded 
anterior end before joining the broadly and regularly rounded ventral margin. 
Posterior dorsal margin long, sloping, nearly straight, forming a rounded angle 
where it meets the posterior ventral margin, which is distinctly incurved, cor- 
responding to a slight but well-marked furrow extending from the umbos. 
The ligamental area is wide, sunken, tapering regularly towards either end, 
with a conspicuous ligament extending half its length. The surface is covered 
by irregular concentric lines and ridges, which, on the umbos, are nearly uni- 
form in size and about equally separated, but below become very irregular and 
are covered with a thin light yellow epidermis decidedly wrinkled by the con- 
spicuous lines of growth, most evident on the ends of the valves; in the centre 
it forms several (six in the type specimen) conspicuous, distant lamelliform 
ridges, the last one very near the edge. Interior bluish white, slightly lustrous, 
with numerous microscopic radiating striz, most clearly defined near the mar- 
gin, and a conspicuous concentric ridge situated half-way between the margin 
and the pallial line. Scars clearly defined. Hinge plate rather broad and well 
arched, with two prominent divergent, curved, cardinal teeth in the right 
valve, and a single thick, equally prominent one in the left valve. The an- 
terior tooth in the right valve is more than twice as thick as the posterior, and 
has a well-marked central groove ; the posterior one is situated directly beneath 
the beak, and is thin, curved, with the concave surface forward and the summit 
broadly rounded; the tooth in the left valve is about equal in size to the an- 
terior one in the opposite valve, and also has a rather deep, central groove. 
Length, 31 mm.; height, 27.5 mm.; thickness, about 13.5 mm. 
This species has been carefully compared with authentic specimens of L. filosa, 
borealis, Pennsylvanicus, and Jamaicensis, but is quite distinct from all of them. 
It is readily distinguished by the irregular concentric sculpture, conspicuous 
epidermis, large lunule, long, broad, nearly straight ligamental area, and con- 
spicuous ligament. 
