248 NEW FOSSIL SHELLS 
Shell conical, somewhat elevated, thin, diaphanous, costate; coste longitudinal, noduliferous, alternate; apex 
produced, incurved, with one whorl, deflected to the left; foramen elliptical; aperture quadrate, oblong. 
Height .04. Length .07. Breadth .05 of an inch. 
Remarks.—The nodules on the ribs are placed in regular series, giving the effect 
of cancellating transverse strie. The ribs are alternately large and small, which, I 
believe, is the case with all our fossil species of these shells. The foramen is widely 
elliptical, approaching to circular, and placed at some distance posterior to the apex. 
The apex is large, bent to the left, and twisted into rather more than one whorl. The 
shell is not much elevated. 
But two species of this interesting little genus have been hitherto described. One, 
the C. noachina, Leach, is from the coast of Great Britain, the other, C. princeps, Mighels 
and Adams, from that of New England. ‘The one now before us is, I believe, the first 
fossil species. It differs from the others principally in its minute size, the absence of an 
internal plate, and the circular form of the foramen. 
GENUS CALYPTRAA. 
C. Pinrouus, Pu. 35. Fic. 38. 
C. testé irregulariter conicd, crassd, sulcatd; sulcis radiantibus, magnis, irregularibus ; striis concentricis, par- 
vis ; apice levi, contorto anfractibus duobus; apertura sub-rotundd ; cyatho magno, lato, angulato. 
Shell irregularly conical, thick, sulcate; sulci radiating, large, irregular; concentric strie minute, small; apex 
smooth, twisted into two whorls; aperture sub-rotund; cyathus large, wide, angular. 
Diam. .80. Height .40 of an inch, 
Remarks.—This species varies very much both in outline and height, some specimens 
being nearly flat, while in others the perpendicular distance from the apex to the base is 
nearly as great as the diameter. The cyathus is large, bent at a right angle, and fast- 
ened to the sides of the shell by the two edges. The sulci vary very much in different 
specimens, both as to number and size. 
In general outline, this shell is not unlike the Dispotea costata, Say, but the form of 
the cyathus separates it from the Dispote, and it also differs in proportionate height. 
Young specimens are not unlike, in external appearance, the Infundibulum concentri- 
cum, herein described, as nearly the upper half of the shell is smooth. 
The peculiar voluted form of the apex, which may also be observed in the Dispotea 
costata, Say, and D. ramosa, Con., would almost seem to entitle them to a separate division, 
were it not that in this family the form of the shells is by no means a criterion for that 
of the animal, and therefore, until the latter has been examined, no separations should 
be made. M. Lesson and Mr. Owen, who have dissected the inhabitants of these shells, 
both say that the difference between the animal of Calyptrea and Crepidula is by no 
means sufficient to establish a generic distinction. Mr. Owen, in a paper read before 
the Zoological Society, observes, “The soft parts of Crepidula are the same with those 
of Caly ptrea, in all essential points of structure, differing only in the proportionate extent 
of the anterior part of the foot, and dorsal groove of the mantle.” M. Lesson,* as quoted 
* Zoologie de la Coquille, Tom. II. p. 388. 
