138 AMERICAN MARINE CONCHOLOGY. 
2. P. BirruNoATA, Conrad. Fig. 321. 
(Glycimeris.) Proc. Philad. Acad., 216, t. 7, f. 1. 1872. 
P. Americana, Conrad. Coues in Proc. Phil. Acad., 139. 1871. 
Shell short, rhomboidal, ventricose, contracted, and obliquely 
truncated anteriorly ; posterior margin oblique, slightly emargi- 
nate, cardinal tooth in right valve small, compressed, flattened on 
the posterior side; pallial sinus widely and obtusely rounded. 
Fort Macon, N. C@. 
A single valve only was received by Mr. Conrad ; and I suspect 
that it is from a submarine fossil deposit, although Mr. Conrad 
thinks it recent. 
Genus CYRTODARIA, Daudin. & 
Journ. de Phys. 1799. 
The animal is larger than the shell, subcylindrical; mantle 
closed, siphons united, protected by a thick envelope ; orifices 
small; pedal opening small, anterior; foot conical; palpi large, 
striated inside, the posterior border plain; gills large, extending 
into the branchial siphon. 
There are two species, extensively distributed through the Arctic 
Seas. 
1. C. stziqua, Chemnitz. Figs. 316, 317. 
(Mya.) Conch. Cab., xi. 192, t. 198, f. 1934. 
Glycimerus incrassata, Lamarck. Syst. An. s. Vert., 126. 
Transversely oblong, compressed, heavy and solid ; epidermis 
thick, shining, obliquely wrinkled ; beaks not prominent, eroded ; 
ligament large, prominent on the shorter end. Interior with a 
very thick callus in the course of the pallial impression ; callus of 
the hinge broad and prominent. Shining black; under the epi- 
dermis ashen gray. 
Length 3.5, height 1.5 inches. 
Massachusetts, northwards. (Hur.) 
Genus SOLEMYA, Lamarck. 
Anim. s. Vert., v. 488. 1818. 
The mantle lobes are united behind, with a single, hour-glass 
shaped, cirrated, siphonal orifice ; foot proboscidiform, truncated 
and fringed at the end; gills forming a single plume on each side, 
with the laminze free to the base; palpi long and narrow, nearly 
free. 
The animal is very active, leaping and swimming rapidly. The 
