Occasional Papers of the Museum of Zoology 43 



Distribution: Bonaire; the higher limestone hills, from 

 Montagne and Seroe Largoe north to Fontein and east (at 

 least) to Seroe Wassau (B3, 4, 5, 6, 8). In the more humid, 

 wooded places; buried rather deeply under rocks and in the 

 crevices of the talus. 175 adults collected. 



Shell (fig. viii-22) : small, elongate-conic, thin. Color: light 

 to dark brown, with about 8, chocolate-colored, spiral bands, 

 usually broken into rows of flammulations. Whorls: Q^o (i^^ 

 a complete male), of which a, little less than 4 are usually 

 retained; cylindrical, with very deeply impressed sutures; 

 last 1/2 whorl descending, slightly tangential, gradually con- 

 stricted, and solute. Last whorl : growth sculpture of crowded, 

 regular, low, rounded threads, interspersed with more promi- 

 nent riblets, at intervals which appear to correspond to resting 

 periods as they are crowded closely together near the per- 

 istome ; spiral sculpture only visible under lens, not especially 

 prominent in umbilical region, consisting of widely-spaced, 

 fine threadlets, w^hich sometimes crenulate the growth threads, 

 but are more commonly obscured by them. Earlier whorls: 

 sculpture somewhat more prominent. Umbilicus : small, tubu- 

 lar. Aperture : circular ; internally light colored. Peristome : 

 simple, continuous; scarcely, if at all, thickened. 



Operculum (figs, viii-23, 24): 414 whorls; almost circu- 

 lar; nucleus subcentral, but slightly nearer the basal angle; 

 chondroid plate inconspicuous, markedly concave internally; 

 calcareous portion thick, solid, and with channeled perimeter; 

 external surface (calcareous plate) distinctly convex, larger 

 than the chondroid plate, and marked by fairly prominent 

 growth-wrinkles. 



Radula (fig. xi-40) : C/1 : Ll/1 + 1/5 ; M/40-41. Central: 

 base very heavy, forming a truncated, isosceles triangle ; single 

 cusp hea\y but slender, almost aculeate. Inner lateral : similar 

 to central but asymmetrical, with inner side longer than outer. 

 Outer lateral : with long, rectangular base ; anterior reflection 

 with 5 stout, aculeate cusps; the transverse thickening under 

 the reflection is very heavy, so that it produces a marked 

 angulation of the sides of the base (as viewed in profile). 

 Marginal : relatively heavier than in Tudora s. s. 



