102 
United States. Cabinet of tbe Academy and Pbiladelpbia Mu- 
seum. 
A very common sbeil on almost all parts of our coast. 
Mactra oblonga. — “Shell transverse^ oblong-oval ; very slightly 
wrinkled, excepting upon the margin j umbo hardly prominent ; two 
strong distant lines or folds drawn from the apex to the anterior 
extremity of the shell; color dull whitish, hardly polished, umbo 
slightly tinged with ferruginous, within white, highly polished. 
Length nine-twentieths of an inch. Breadth one inch and 
nine-tenths. Inhabits the coast of Gleorgia. Cabinet of the 
Academy and Philadelphia Museum. 
Of this species I found but three valves, on one of the sea 
islands of Oeorgia. 
Lutraria lineata.— Shell transversely suboval, thin white, 
tinged with ferruginous; posterior hiatus patulous, anterior one 
linear and commencing below the hinge slope ; hinge slope with a 
rectilinear profile, and flattened, oblong-sub cordate surface ; valves 
unequally wrinkled ; posterior margin rounded, short, with a re- 
flected edge, and submarginal carinated line ; within undulated, 
anterior margin glabrous, and with an indented submarginal line 
corresponding with the exterior carinated one. 
Length one inch and nine-tenths. Width two inches and seven- 
tenths. Thickness one inch and one-twentieth. Inhabits the 
coasts of G-eorgia and East Florida. Cabinet of the Acaderiiy and 
Philadelphia Museum. 
Not uncommon on the southern coast, and may be readily dis- 
tinguished by the carinated line on the posterior submargin. 
Lutraria canaliculata. — ^Shell transversely oval-orbicular, 
very thin and fragile, white, inflated ; valves equally, concentri- 
cally, and regularly grooved, very feint parallel lines within the 
grooves ; posterior margin short, subcuneiform, compressed ; a mar- 
ginal, longtudinal, irregular, subimpressed line, between which 
and the edge the grooves become mere wrinkles ; posterior slope 
subrectilinear, hiatus considerable ; anterior margin regularly 
curved, the slope convex; within grooved as without, anterior 
angle glabrous. 
Grreatest length two inches and one-twentieth. Breadth two in- 
ches and a half. Thickness one inch and one-fourth. Inhabits 
the coast of the United States. Occurs on the coast of Maryland 
