OF CONCHOLOQY. 305 



2. Chondropoma Navassense, Trjon. — 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 m 

 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 



