Some New Species of Marine ‘Shells. 285 
ART. XVIII. — DESCRIPTIONS OF SOME NEW SPECIES OF MARINE 
SHELLS, INHABITING THE COAST OF THE UNITED STATES. 
By Henry C. Lea, Philadelphia. Read Nov. 20, 1844. T 
Puonas semicosrara. Pl. XXIV. Fig. 1. Proceed. Bost. 
Soc. Nat. Hist. Nov. 1844. 
P. testa sub-triangulari, posticé producta et want, anticé oblique truncata, 
tenui, albidá, diaphaná, anticé inflata et costatá; costis transversalibus, 
muricatis, magnis, crebris, posticé obsoletis; sulco uno longitudinali, a nati- 
bus decurrente ; margine basali eurvato ; margine-dorsali vix recto; natibus 
valde inflatis; lamina dorsali parva ; cochlea ligulata, acutissima, incurvà. 
Shell sub-triangular, posteriorly produced and acute, ob- 
liquely truncate anteriorly, thin, whitish, diaphanous, anterior- 
ly inflated and costate; ribs transverse, muricate, large, nu- 
merous; posteriorly obsolete; one longitudinal sulcus running - 
from the beaks; basal margin. curved ; dorsal margin almost 
straight; beaks very much inflated; dorsal plate small; 
cochlea ligulate, very acute, incurved. Long. .17. Lat, .32. 
Diam. .16 poll. 
Hab. South Carolina. 
Remarks. The transverse ribs are rather large, very regu- 
lar, and distant from each other about their own width. 
They are muricate, or covered with small, arched scales, from 
the anterior margin to the longitudinal sulcus, when they 
suddenly become smooth, and soon after disappear. The 
rest of the shell has a few small, transverse lines of growth 
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"I of the area of the shell, extending from the beak nearly 
to the basal margin, and from the anterior margin a little 
more than one-half to the posterior end, is somewhat in- 
crassated, and raised above the surrounding surface. To this 
