240 CERION, GROUP IX. 



IX. Group of O. gubernatorium. 



Shortly rimate shells, tapering, oval or sometimes cylindric, the- 

 upper part generally smooth, last whorl or two usually ribbed ; pari- 

 etal tooth usually somewhat long; peristome built forward and 

 beveled when thick, the parietal callus either appressed or forming 

 a raised ledge. 



These forms are never strongly and regularly ribbed like specie* 

 of the group of C. glans, but they are clearly related to that group 

 by the frequently beveled lip which may be built forward, the 

 occasionally ridge-like parietal callus, and the short umbilical chink. 

 Some forms have a blue streak at the base such as is frequent in 

 C. glans. They inhabit keys and islands of the Great Bahama 

 Bank, from Eleuthera and New Providence on the northeast, south- 

 ward to Exuma, and in the west, some small keys bordering Florida 

 Strait. 

 a. Parietal callus forming a strong, raised ridge. 



b. Finely striate. Duck Key, Exuma Group. 



C. milleri, p. 243. 



b 1 . Last whorl ribbed. New Providence. C. agassizi, p. 242. 

 a 1 . Parietal callus appressed, not ridge-like. 

 b. Interior, and usually the lip, brown. 



c. Shell smooth, or with the last whorl striate; rather 

 thin, usually variegated. New Providence. 



C. gubernatorium, p. 242- 



c 1 . Last one or several whorls ribbed ; stouter ; generally 

 whitish. Eleuthera. C. eleuthera, p. 240. 



c 2 . Nearly smooth, whitish. Water Cay. 



C. niteloides, p. 244. 

 b 1 . Interior and lip white ; parietal tooth small. Gun Cay. 



C. pillsburyi, p. 244. 



C. ELEUTHERA Pilsbry and Vanatta. PI. 36, figs. 35, 36, 37, 38. 



Shell solid and strong ; smoothish above, ribbed below ; lusterless ; 

 white, with a bluish-purple tint, most obvious around the base. 

 Cylindric-tapering, terminating above in a rather long slightly con- 

 vex-sided cone which passes gradually into the cylindrical portion, 

 or the whole shell may taper to the last whorl. Apex obtuse ; whorls 

 10^ to 12^; nepionic 2^ whorls nearly smooth, slightly convex; fol- 

 lowing whorls of the cone smoothish to the naked eye, showing rather 



