272 CERION, GROUP XIII. 



In the present stage of evolution of these organisms, such varia- 

 tions are not specifically or even varietally constant, except in the 

 average. Adult individuals living side by side may exhibit various 

 tooth arrangements, although the greater number of individuals in 

 any given colony will agree. The grouping of the various local 

 forms into conventional " species " is more or less arbitrary. 



Key to Species of Inagua. 



1. A rather short parietal lamella or none; no deeply- entering spiral 

 lamellae; length 16-23 mill. 



a. Dark brown with white ribs, or maculate, bryanti, p. 272. 

 01. Dull purple with white ribs, roseate above, pudicum, p. 273. 



2. A denticle inward from the parietal, and another towards the axis ; 

 length 14-15 mill.; densely, finely striate. heterodon, p. 275. 



3. Two very long parallel spiral lamellae running within from the 

 parietal lamella. 



a. Roseate above, purplish with white ribs below ; length 22- 

 25 mill.; riblets 23 to over 40 on penult, whorl. 



rubicundum, p. 274. 



a 1 . Flesh-tinted with white riblets or brown and white macu- 

 late ; length usually 30-36 mill., riblets 27-73. 



dalli, p. 276. 

 a 2 . White variegated with gray, the aperture white within. 



duplodon, p. 276. 



C. BRYANTI (Pfeiffer). PI. 46, figs. 5-10, 13-16. 



Shell shortly and deeply rimate, subperforate, oblong, solid ; 

 chestnut colored, with obtuse, white, rather distant riblets. Spire 

 tapering in a somewhat obtuse cone, the apex pale corneous. Whorls 

 9 to 10, a trifle convex, slowly increasing, the last slightly ascending 

 in front, somewhat compressed around the umbilical fissure. Aper- 

 ture vertical, sub- oval, dark chestnut colored within ; parietal fold 

 small and deeply situated, columellar fold obsolete ; peristome white, 

 somewhat thickened, and narrowly reflexed, the margins joined by a 

 whitish callus; right margin arcuate, the columellar margin dilated 

 above. Length 18J to 21, diam. 7 mill.; aperture with peristome 

 7^ mill, long,' 6 wide (Pfr.~). 



Southern part of Inagua (W. W. Miller). 



Pupa bryanti PFR., Malak. Bl., xiv, 1867, p. 130 ; Novit. Conch., 



