92 Hemarhs on Certain Species of 



Shell nmbillcate, orbicular, horn-colored or pale rufous, above 

 flat, obliquely and acutely ribbed, beneath convex, slightly 

 striated, shining, often ornamented with indistinct white spots; 

 suture deeply impressed ; whorls 5|-6|^, the last subangular at 

 the periphery, shortly but suddenly deflected at the aperture, 

 gibbous, scrobiculate, constricted, tumid behind the aperture, 

 and ribbed, base dilated, with a white internal lamina on the 

 columellar wall near the point of attachment of the aperture ; 

 aperture very oblique, lunate ; perist. callous within, thickened, 

 little reflected, the margins joined by a triangular dentiform 

 lamella. 



Diam. maj. 10, min, 9, Alt. 4 mill, anfr, 6|. 

 " " 7, " 6, " 3 " " 5i, 



Hahitat. — Ivey Biscayne, Florida, Wurdeman ! Key West, 

 Shuttleworth. South Florida, Dr. Cooper ! Sea Islands, Flo^ 

 rida, Bartlett. Lake Harney, Fla., E. Norton ! 



Remarks. — This species has been hitherto named II. micro- 

 donta Desh. in American Cabinets, and I have indeed so 

 distributed it, but I believe erroneously. It is readily distin- 

 guished from all the other species of the group by its strong 

 acute rib-like stride, and the peculiarity of the outer whorl. 

 About the last third of it, behind the aperture, is ribbed and 

 tumid, — the whorl is then rather abruptly contracted, becoming 

 narrower above, and flattened and slightly striated beneath, but 

 again, as it passes towards and beneath the aperture, dilated, 

 and convex. This change of form gives to the last whorl a 

 distorted appearance. Tlie internal lamina is on the columel- 

 lar wall of the contracted and flattened portion of the last whorl, 

 and runs obliquely, in the direction of the aperture, attaining a 

 length in a large specimen of about 6 mill. The character of 

 the aperture is most like that of H. oereolus^ but in that species 

 the last whorl has none of tlie peculiarities above described. 

 The internal lamina is found in a majority of specimens, but 

 not in all; it can generally be seen through the outer wall of 

 the shell. 



