OF CONCHOLOdY. 305 



2. Chondropoma Navassense, Tryon. — t. 20, fig. 12. 



Description. — Ovately turrited, moderately thick, slightly 

 truncate, covered with numerous close, sharp revolving lines 

 decussating the almost equally prominent ridges of growth, 

 and becoming more distinct towards the base; sutures exca- 

 vated and minutely crenate-margined ; aperture suboval, the 

 outer lip expanded, but not reflected, produced angulate above, 

 and rounded angulate below, the labrum laying close on the 

 body-whorl, and almost entirely covering the umbilicus. 

 Light horn-color or nearly white (bleached ?) 



Dimensions. — Alt. 18 (truncated), diam. 12 mill. 



I have seen five specimens of this shell, of which one, from 

 Prof. F. V. Hayden, appears to be fossil. Although no oper- 

 cula were preserved, there is little doubt but that it belongs to 

 the genus Chondropoma, a genus which is present both in 

 Cuba and Haiti, but not represented in Jamaica, thus showing 

 the alliance of the fauna of Navassa with those of the two 

 former islands. 



3. Helicina circumlineata, Tryon. — t. 20, fig. 13. 



Description. — Elevated, conical, apex mucronate ; whorls 6, 

 covered with close revolving lines, the last one having about 

 twenty above the subangulate periphery, and smaller, closer 

 lines on the base below it ; lip slightly expanded and much 

 thickened. White or somewhat flesh-colored (denuded). 



Dimensions. — Height 9, diam. 9 mill. 



Two specimens are before me, both evidently recent, al- 

 though bleached, and destitute of opercula 



