S6 LAND AND FRESII-WATER SHELLS OF X. A. [PART III. 



peristome simple, or more or less thickened, somewhat straight, 

 rather expanded or broadly reflected. 



Fig. 192. 



Chondro- 



poma 

 denlatum. 



Clioiiilropoma dentatum, Say. — Shell conic cylindrical, or 

 tuireted, truncate at tip, the surface finely cancellate with 

 raised, longitudinal, and revolving lines ; color varying from 

 yellowish to brown, usually with darker brown bands, which 

 are generally interrupted in such a manner that the colors 

 also form longitudinal stripes ; whirls, when complete, seven ; 

 but the three uppermost are usually lost ; they are rounded, 

 and separated by a deep, crenulated suture ; aperture rounded 

 ovate, a little angular posteriorly ; peristome a little reflexed, 

 white ; base with a minute perforation. Length 12, breadth 

 4 mill. 



Ci/closioma dentatum, Sat, Journ. Phila. Ac. V, 125 : Binnet's 



ed. 29.— DeKay, N. Y. Moll. 82.— Binney, Terr. Moll. II, 348, pi. Ixii. 

 Chondropoma dentatum, Pfeiffer, Mon. Pneum. Viv. I, 286 ; II, 140 ; Mai. 



Blatt. 1856, 132.— Gray & Pfeiffer, Brit. Mus. Cat. Phan. 203.— 



W. G. BiNNEY, Terr. Moll. IV, 91, pi. ixxv, f. 24. 



Key West : Fort Dallas, Florida. 



Animal (see Fig. 190) : Body very short, pale, tentacles darker, 

 slender, somewhat enlarged at tips ; eyes black, prominent, situ- 

 ated on a tubercle at the external base of the tentacles. Pro- 

 boscis bifurcate, the two points serving the purpose 

 of buccal tentacles. Operculum horny, the spiral of 

 about two and a half turns. 



The shell is carried somewhat laterally, and very 

 little elevated. The motions of the animal are very 

 rapid ; the locomotive disk contracts in an undulatory 

 mannef ; and when the animal has advanced so that the shell 



drags along by its side, by a sudden 

 contraction of the neck the tip of the 

 shell is suddenly jerked forward, so as 

 to bring the shell at right angles with 

 it; and this movement, in a quarter 

 of a circle, is very rapidly performed. 

 As the operculum prevents the animal, 

 when at rest and retired within its 

 shell, from adhering by means of its 

 foot, as is usual with the Helicidfe, 

 c. deTitatum at rest, enlarged. the auimal has the powcr of spinning 



Fig. 193. 



Operculum of 

 C. dentntum. 



Fig. 194. 



