220 



CERION, GROUP VI. 



lines like those of the present group, though less conspicuously de- 

 veloped. 



a. Shell conspicuously tapering, the whorls very convex. Cuban 

 species. 



b. Spire rather thick above ; whorls 9J-101 ; alt. 17-18 mill. 



scalarinum, p. 223. 

 ft 1 . Spire much attenuated above; whorls 11^; alt. 32 mill. 



johnsoni, p. 223. 

 a 1 . Shell cylindric, conic above. 



b. Whorls very convex, 10 ; teeth small ; 22x9 mill.; Cuba. 



sueyrasi, p. 222. 

 ft 1 . Whorls rather flattened. 



c. Umbilicus small ; ribs continued on the base ; whorls 

 10J; 28x111 mill.; Cat Island. felis, p. 221. 



c 1 . Umbilicus wide ; base usually ribless ; whorls 810 ; 

 27x12 to 21x14^ mill. Berry Island, Bahamas. 



stevensoni, p. 220. 

 c 2 . Whorls 8; 22x11 mill. sculptum, p. 222. 



C. STEVENSONI Dall. PI. 44, figs. 70, 71. 



Shell very variable in general form, but in general roughly cylin- 

 drical, with the nuclear whorls as it were jammed down into the 

 blunt summit of the cylinder, with the base carinate at the periphery, 

 where the ribs cease, and below that constricted ; whorls 8-10, 

 nuclear ones nearly smooth, gradually developing fine transverse 

 ribbing with subequal interspaces; these become stronger, with a 

 strong revolving thread behind the suture ; at the third whorl then 

 the diameter of the shell suddenly increases, the sides develop strong 

 transverse rather irregular ribbing with wider interspaces, the ribs 

 extending from the suture to the basal keel, beyond which they 

 rarely extend ; the base beyond the keel is constricted, rudely trans- 

 versely wrinkled, inside the verge of the umbilicus centrifugally im- 

 pressed and axially deeply perforate ; aperture very variable in shape, 

 with a broad, flattish, rather thin reflected margin; there is a parietal 

 short lamina centrally situated and strong, but no trace of an axial 

 fold ; color light brownish or ashy to white, the whole surface sharply 

 spirally striated, the strias sometimes crowded, sometimes distant. 

 (Dall.) 



