HELIX. 



241 



very thin, transparent ; whorls five, prominent, -with 

 exceedingly minute, oblique striae of increase ; suture 

 deeply impressed ; base somewhat convex ; axis open, 

 umbilicus infundibuliform ; aperture flattened-transverse ; 

 lip thin, acute, not reflected. 



Greatest diameter one-fifth of an inch. 



GEOGRAPHICAL DISTRIBUTION. Inhabits the southern 

 parts of Florida, and the islands adjacent ; also the 

 island of St. Croix. 



REMARKS. This small species does not exceed Helix 

 arbor ea in size. Its transparency is greater than that of 

 any other of our species. The general character of its 

 upper surface is that of depression ; but though the 

 whorls revolve in nearly the same plane, the suture is so 

 deeply impressed that each whorl is rendered convex, or 

 tumid. The umbilicus is of small diameter, but well 

 defined and deep. The aperture is transverse, and flat- 

 tened in its vertical diameter ; the lip is thin, sharp, and 

 not turned outwards. The convexity of the base being 

 greater than that of the upper surface, an obtuse angle 

 is sometimes produced on the periphery of the shell at 

 the line of their junction, which is more or less prominent 

 in different specimens. 



This shell is obviously identical with a Helix brought 

 from the island of St. Croix by Dr. R. E. Griffith, and 

 distributed by him to several cabinets in the United 

 States. There can hardly be a doubt that it exists in 

 some of the other West Indian Islands. Specimens have 



VOL. II. 31 



