134 BULLOETEN 181, UNITE© SITATEIS NlATIOOSIlAiL MUSlEIUM 



wavy, slender, raised, retractively slanting axial threads, which are 

 disposed in a more or less zigzag pattern, and lend to the surface 

 a worn-file effect. Suture well constricted. Periphery somewhat in- 

 flated, strongly rounded. Base strongly rounded, marked by the 

 continuation of the sculpture described for the spire. Umbilicus 

 broad, open. Aperture almost circular, somewhat angulated at the 

 posterior angle; peristome thin, slightly reflected, a little thicker on 

 the columellar wall, adnate to the preceding turn at the parietal wall. 

 Operculum typically austrocyclotid. 



The specimen described and figured, U.S.N.M. No. 535919, was col- 

 lected by Bartsch on Mount St. Andrews, St. Vincent. It has 4.4 

 whorls and measures : Height, 13.7 mm. ; greater diameter, 22.7 mm. ; 

 lesser diameter, 17.1 mm. 



This species recalls most nearly 4. (A.) grenadense (Shuttle worth), 

 from which its much larger size will readily distinguish it. 



APEROSTOMA (AUSTROCYCLOTUS) GRENADENSE (Shuttleworth) 



Shell small, depressed-helicoid, openly moderately broadly umbili- 

 cated. Nuclear whorls about 2, well rounded, smooth, conforming in 

 increase with the rest of the spire. Postnuclear whorls slightly flat- 

 tened near the suture, the rest well rounded, marked by incremental 

 lines and obliquely slanting, low, elongated tubercles, which lend the 

 surface a wrinkled appearance. This sculpture usually weakens to- 

 ward the last tenth of a turn, where the incremental lines become 

 much rougher and irregular. Periphery of last whorl well rounded. 

 Base strongly rounded, marked like the spire. On the umbilical wall 

 the tuberculations may weaken. Aperture broadly ovate, somewhat 

 pointed at the posterior angle. Peristome acute. Operculum of about 

 six whorls, typically austrocyclotid. 



The species appears confined to Grenada. I am recognizing two 

 subspecies : 



KEY TO THE SUBSPECIES OF APEROSTOMA (AUSTROCYCLOTUS) GRENADENSE 



Base strongly granulose grenadense 



Base not strongly granulose mcsweeni 



APEROSTOMA (AUSTROCYCLOTUS) GRENADENSE GRENADENSE (Shuttleworth) 



Plate 17, Figures 19-21 



1857. Cyclostoma (Cyclotus) grenadense Shuttleworth, Journ. Conchyl., vol. 5, 

 p. 266. 



This subspecies is differentiated from Aperostoma {Austrocyclotus) 

 grenadense mcsweeni by having the base strongly granulose. 



