CERION, GROUP V. 205 



for typically developed specimens, and of course is quite artificial. 

 a. Shell of robust, broad contour. 



b. Smooth on the cone or throughout. 



c. Diameter over half the length ; cone very short; whit- 

 ish ; ribbed or smooth. dimidiatum, p. 205. 

 e 1 . Smooth or nearly so ; richly variegated, torrei, p. 207. 

 b l . Ribbed throughout. 



c. Unicolored, usually snow-white. muliicosta, p. 208. 

 c 1 . Bluish ; lip very thick, sinuous above. 



incrassalum, p. 207. 



c 2 . Variegated with brown. ornatum, p. 208. 



a 1 . Shell moderately stout, the diam. usually contained 2^ times or 

 more in the length. 



b. Interior rich purple. iostoma, p. 210; arangoi, p. 211. 



6 1 . Parietal tooth long. 



c. Shell long and slender. hyperlissum, p. 211. 



c 1 . Shell rather short. longidens, p. 212. 



b 3 . Without either of the above characters. 



c. Shell slender, richly variegated with purple-brown ; 

 lip narrow. vulneratum, p. 219. 



c 1 . Shell moderately stout in Hgure. 



d. Cone short; parietal tooth doubled or buttressed. 



politum, p. 217. 

 d 1 . Cone longer; parietal tooth simple. 



e. Species of Florida Keys and Bahamas. 



incarmnii p. 213. 



e 1 . Species of Cuba. maritimum, p. 212. 



sagraianum, p. 216. 



C. DIMIDIATUM (Pfeitfer). PI. 28, figs. 27-32. 



Shell perforate and rimate, solid, cylindric, very obese, often widest 

 above, white or whitish. Whorls about 10^, the first one smooth, 

 the next two finely and densely striate, the rest of the whorls of the 

 very short, wide cone nearly smooth, fiat ; last three whorls forming 

 the cylindrical portion, sculptured with curved ribs, which vary from 

 strong and regular to irregular, or they may even be completely ab- 

 sent. A group of spiral incised lines may usually be seen below the 

 middle of each whorl. Last whorl ascending in front, having the 

 rather flattened base defined by a revolving cord (sometimes obso- 



