FROM THE TERTIARY OF VIRGINIA. 249 
by Mr. Broderip, says, “ L’animal des Calyptrées et des Crépidules nous parait ne dif- 
ferer en rien d’essentiel; et quant a la cloison du test, soit que cette cloison soit trans- 
versale, soit qu ‘elle ne consiste qu ’en lamelles anexées au fond de la coquille, elle pre- 
sente des passages de ces deux étits, et ne peut servir qu ’é etablir des simples sous- 
genres, au grand genre Calyptrea ou Crepidula comme on voudrait l’appeler.” I have 
therefore put the following shells as merely in sub-genera. 
SUB-GENUS INFUNDIBULUM (Dx Monrrort.) 
I. concentricum, Pu. 35. Fic. 39. 
1. test patelliformi, depresso-conicd, tenui, simplici; lineis minutis concentricis; apice centrali, anfracts parvo uno; aper- 
iurd sub-rotundd; cyatho recto, varice marginato. 
Shell patelliform, depressed-conical, thin, simple; with minute concentric lines; apex central, with one small 
whorl; aperture sub-rotund; cyathus straight, margined with a varix. 
Diam. .22. Height .09 of an inch. 
Remarks.—This shell is entirely simple and patelliform, with the exception of one 
small whorl at the apex. The cyathus is flat and straight, extending from the centre to 
the margin, with a thick varix at its outer edge. 
The only Infundibulum, to which this is allied, is the I. centrale, Con., but that 
species is described as ovate, while this is conical, or even slightly concave. 
This is one of the shells that show the gradual passage from the Infundibulum to the 
Crepidula, and the propriety of uniting these genera. Its want of whorls, and the con- 
centric lines of growth, seem to place it in the Calyptrax, while the cyathus constitutes 
it an Infundibulum. 
SUB-GENUS CREPIDULA. 
C. ponpEerosa, Pu. 35. Fic. 40. 
C. testd sub-globosd, crassissimd, ponderosa, convolutd, rugosa; sulco prope suturam lato, minime profundo; suturd parva; 
apice voluto, rotundato, anfractibus sesqui; apertura arctato ellipticd; cyatho crassissimo, undulato, acie flecuosd, via aperture 
dimidiam equante. 
Shell sub-globose, very thick, ponderous, whorled, rugose; with a wide, shallow sulcation near the suture; suture 
small; apex voluted, rounded, with a whorl and a half; mouth narrow-elliptical; cyathus very thick, undulate, with 
a flexuose edge; scarcely half the length of the mouth. 
Height 1.15. Length 1.90. Breadth 1.50 inches. 
Remarks.—There are occasional irregular lines of growth over the surface. The sul- 
cation near the suture is sometimes scarcely perceptible. It usually continues for about 
one third of a whorl from the aperture, and then becomes obsolete. ‘The mouth is some- 
times very small and nearly round. The cyathus is extremely solid with two depres- 
sions on its surface and a waved edge. It is deeply set in the shell, and disappears 
gradually into the sides, so that its margin cannot be traced. The apex is more voluted 
than in any species of Crepidula that I have met with. 
This fine shell has, most probably, been heretofore confounded with the C. costata, 
Morton, as it is too common and too conspicuous to have escaped observation, and as there 
are specimens of both under that name in the collection of the Academy of Natural 
VOL. IX.—66 
