longed upon the tubes and edges of the mantle of the animal, 
tolerably solid, with fine trenchant edges, the summits very little 
marked, hinge dissimilar, one or two oblique cardinal folds, di¬ 
vergent, behind a horizontal spoon-shaped hollow apron, the left 
valve corresponding with a hollow horizontal and cardinal in the 
right valve, two distinct muscular impressions. Ten species, of 
which four are American. I have had several conchologists in 
Europe ask me if it were really true that this species was eaten in 
America. I have always referred them to a Rhode Island clam 
bake. 
Alactragigantea or deep sea clam.—The Mactra has a peculiar 
hinge distinguishing it from all other genera. It is triangular, 
with a curved or angular compressed tooth on each valve, with a 
small oblique cavity on each side, to which is attached the liga¬ 
ment. Two lateral teeth, one near the primary tooth and one 
near the ligament. The shape of the shell is subtriangular or ob¬ 
long, exterior smooth, straited or ribbed transversely, two muscu¬ 
lar impressions united by a narrow marginal tongue. Forty-four 
species, thirteen of which are American. 
In conclusion I would call your attention to a specimen of the 
fresh water Unto from Easton’s pond, and also to an oyster shell, 
the property of a gentleman here in town, who has been kind 
enough to loan it to me for this occasion. It is undoubtedly 
the most patriotic shell in existence and the owner values it ac¬ 
cordingly. It has the letters U. S. perfectly formed by the Ser- 
pula contortuplicata. 
