Fossil and Recent Shells. ‘S41 
CORBULA. 
1. C. idonea.’ Shell subtriangular, convex, thick, obscurely un- 
dulated ; with a fold on the posterior sub-margin and the extremity 
angular; basal margin acute; cardinal tooth very thick and elevated. 
Length, one inch. 
Locality.—Choptank river near Easton, Md., common; Upper 
2. €. oniseus. Shell elevated; larger valve ventricose, with pro- 
found sulci terminating at the umbonial slope, which is carinated ; 
posterior extremity narrowed and truncated, from the posterior ankle 
of which a carina extends to the apex, nearly parallel with that of 
the umbonial slope ; superior valve concentrically striated. Length, 
one third of an inch. 
“Locality.—Claiborne, Alab. London clay. 
“This species can hardly be distinguished from the C. angustata of 
Sowerby, Geological Trans. 2d series, vol. iii, pl. 38, fig. 4. The’ 
latter was found in the valley of Gosau, Saltzburg Alps. — 
Re eee, ae 
re C. pongrenesa: "Shell dendaals vice Ee 
convex, with numerous erect. elevated arched scales; beaks occa- 
3 apex sub-spiral ; scales on. the cae valve. 
broader tp more elevated; inner margin crenulated. ciplie vehi ceed 
Locality.—James river, near Smithfield, Va. Upper marine. x 
2. C.corticosa. Shell sinistral; with strong concentric undulated 
laminz transversely striated ; superior valve flat; inner margin cren- 
sated. Found with the preceding species. 
a 
ig ee 
PETRICOLA. 
op. eentenaria. Shell oblong oval, with numerous prominent ra- 
diating strie, and concentric wrinkles ; lunule small, iden pro- 
SF apecke,; the middle one bifid. Length, two inches. _ 
Localities —James river near Smithfield, Va.; Choptank river 
near. Easton, Md. Upper marine. 
. PECTEN, 
: P. icici ‘Shell suborbicular, compressed, thin; a little oblique ; 
ribs about twenty two, rounded, little elevated and smooth ; inferior 
valve nearly flat. Length, two inches. ings 
Locality.—Suffolk, Va. Upper marine. 
