248 NEW FOSSIL SHELLS 



Shell conical, somewhat elevated, thin, diaphanous, costate; costae 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 stria?. 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. pririceps, 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 CALYPTR^A. 

 C. PILEOLUS, PL. 35. FIG. 38. 



C. testa irregulariler conicd, crassd, sulcatd; sulcis radiantibus, magnis, irregulartbus ; slrtis concentricis, par- 

 vis; apice leevi, contorto anfractibus duobus; aperturd sub-rotunda; cyatho magno, lato, angulato. 



Shell irregularly conical, thick, sulcate; sulci radiating, large, irregular; concentric striae minute, small; apex 

 smooth, twisted into two whorjs; 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 Dispotaa costata, Say, but the form of 

 the cyathus separates it from the Dispota3se, and it also differs in proportionate height. 

 Young specimens are not unlike, in external appearance, the Infundibulurn 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 Dispotsa 

 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 Calyptrsea 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 Calyptrsea, 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. 



