1896.] NATURAL SCIENCES OF PHILADELPHIA. 331 



whorls of about equal diameter ; apex obtuse ; earlier whorls not 

 striate; chalk-white and dull, the smoothness of the surface but little 

 broken by slight growth-lines, tJie basal whorl irregularhj and rather 

 distanthj costate, at least on its latter half Whorls 10 to lOj, flat, 

 with superficial, seam-like sutures. Last whorl suddenly ascending in 

 front, much compressed and jnnched toward the base. Umbilicus 

 open or perforate, with the usual arcuate rimation, below which it 

 is broadly excavated and flattened. 



Aperture oblong-cordate, slightly less than one-third the length 

 of shell, higher than wide, dark or light brown within, rarely pur- 

 plish. Peristome expanded and reflexed, its face convex but not 

 much thickened, whitish, parietal callus moderate, its outer edge not 

 raised. Axial lamina situated high, narrow and inconspicuous from 

 in front. Parietal tooth low, small, varying from moderately short 

 to long, central in position. 



Alt. 31*,diam. llf mill. 



Alt. 33, diam. 12i mill, (average typical specimen). 



Alt. 38, diam. 13 mill. 



Turk's Island, Bahamas. (Gabb, Swift). 



Cerion sarcostomum Pilsbry & Vanatta. PI. XI, fig. 16. 



Shell solid and strong, subcylindrical, but slightly wider below ; 

 whitish. Whorls 11 to IH, slightly convex, the earlier 6 forming 

 a convexly tapering cone with extremely obtuse apex, almost dome- 

 shaped at top; passing gradually into the cylindrical portion of 

 shell, which consists of 5 to 6 whorls. Sculpture, somewhat irreg- 

 ular and unequal, straight ribs, about as wide as the intervals, about 

 25-30 on last whorl. These ribs are strongly developed on the 

 cylindrical portion of the shell, but the cone is very densely, finely 

 and sharply striated, the earliest whorl only being smooth. 



Aperture small, less than one-third the total length of shell, pink- 

 ish-flesh colored in the throat; peristome well reflexed, recurved, 

 more or less thickened on the inner edge of the face ; parietal callus 

 thick and heavy, its edge elevated. Parietal tooth rather strong and 

 moderately long ; axial fold moderately conspicuous. 



Alt. 34, diam. IH ; alt. of aperture 10 mm. 



Little Inagua, Bahamas. 



Some specimens are larger than the above dimensions ; one worn 

 and broken " crab-shell " before us would probably be not less than 

 40 mm. alt. if perfect. It is not unlikely that forms occur with the 

 ribs obsolete, as in the allied C. columna. 



