246 NEW FOSSIL SHELLS 
This shell may be distinguished from all its congeners of our Tertiary by its small 
and numerous cost, and longitudinal form. 
P. Tenvis, Pu, 35; Fie: 33. 
P. testé sub-orbiculari, aquilaterali, convexd, tenut, striatd; striis radiantibus, crebris, tum magnis, tum parvis , 
lineis concentricis, minutis, raris; natibus acuminatis, sub-elevatis; auribus magnis, inequalibus, striatis; testa in- 
terneé levi, 
Shell sub-orbicular, equilateral, convex, thin, striate; strie radiating, numerous, sometimes large, sometimes small; 
a few minute concentric lines; beaks acuminated, somewhat elevated, auricles large, unequal, striate; shell smooth 
within, 
Diam. .60. Length 2.26. Breadth 2.28 inches. 
Remarks.—The strie are very irregular as to size, and frequently are alternate. Near 
the base they are much smaller; and are decussated by numerous very minute, concen- 
tric lines. On the only valve now before me, they are about one hundred in number. 
The shell has been quite longitudinal when young, as may be seen from the lines of 
growth. Three or four of the longitudinal strie are rather larger than the rest, particu- 
larly near the beaks. 
This pretty shell was found at Shell Bank near Petersburg, the plantation of E. 
Ruffin, Esq., and sent by him to my father. It may be distinguished from P. Clinto- 
nius, Say, a species to which it is closely allied, by its unequal auricles and stria, its 
more longitudinal form, and acuminate beaks. 
GENUS PLICATULA. 
P. rupis, Px. 35. Fia. 34. 
P. testé longitudinali, orbiculari, pland, tenui, rugosd; natibus prominulis, acutis ; dentibus magnis; margine intus 
lato, nigrescente. 
Shell longitudinal, orbicular, flat, thin, rugose; beaks prominent, acute; teeth large, internal margin wide and 
blackish. 
Diam .20. Length .68, Breadth .65. of an inch. 
Remarks.—The surface is nearly covered with irregular Jongitudinal wrinkles, which 
render it very rugose. It is nearly flat and destitute of folds. 
This shell may be distinguished from the P. marginata, Say, which it somewhat 
resembles, by its flat, orbicular form, rugosities, thinness and want of folds. It is much 
rarer than that species. I found but three or four specimens of it among more than a 
hundred of the other. 
FAMILY PHYLLIDIDZ. 
GENUS CHITON. 
4 
C. TRANSENNA, Py, 35. Fic. 35. 
C. testa—, octovalvi? crassd, costatd, dorso valde elevatd et angulatd; valvarum intermediarum ared centrali costis 
longitudinalibus rectis, noduliferis, ared laterali aut levi aut nodulosd; value terminalis ared centrali noduloso 
costatd, ared laterali nodulosd. 
