rior side, about as wide as the interstices, 30 in numbor, with arched scales 
turned towards the anterior end ; anterior area with scales ot a different 
pattern, funnel shaped on very close ribs; posterior margin slightly 
rounded or curved, direct anterior margin truncated obliquely inwards. 
Length 1 34 inches : height nearly 2 inches, or about one-sixteenth less. 
MYSIA. Leach. 
M. Carolinensis , pi. 4, fig. 5. Rounded, inflated, thin, equilateral, 
slightly oblique, posterior end obtusely rounded ; cardinal teeth are one 
direct, situated under the apex, and the other very oblique ; left valve 
with a very oblique bilid tooth ; anterior margin carinated and suddenly 
turned up to the apex. 
PLEUROMERIS. Conrad. 
P. decemcostata. Conrad. A larger specimen of this species than I 
have heretofore seen is in the State cabinet at Raleigh. The hinge char- 
acter approaches that of Woodia, Desk, but the large triangular tooth of 
the right valve is not subcanaliculate like that of Woodia , but deeply and 
angularly grooved the whole width of the tooth, leaving sharp angles on 
the margin ; and there is a small anterior lateral tooth in the left valve, 
an elongated posterior cardinal tooth, also, and profound ribs on the exte- 
rior, and a deeply-impressed small lunule, in which character it differs 
from the allied genus. The crenulations of the inner margin have none 
of the obliquity of Woodia. A fine exotic example of this genus is the 
Cardita ILicxsii, JSTyst. Other species are (J omaliana, Nyst, C. scalaris, 
Sowerby and C. orbicularis , Sowerby, C. chamoeformis , Sowerby, C. ana- 
lis, Phillippi. The genus can be easily recognized by external characters, 
such as its small size, elevated triangular outline, and granulated, radiating 
ribs. It has more the general outline of Crassixa than of Cardita. 
PTERORHYTIS. Conrad. 
This genus, related to the above, comprises 2 small species of the At- 
lantic Miocene compressed triangular short shells, with prominent, radi- 
ating ribs. The left valve has two diverging bifid teeth, with an inter- 
mediate triangular pit, the posterior cardinal tooth being profoundly 
divided ; above the posterior muscular impression is a long, narrow, acces- 
sory one. I have not seen the right valve of either species. 
