PUPA. 317 



pression at the base of the axis; lip -white, thickened, 

 sub-reflected ; base of shell compressed, sub-carinate ; 

 axis imperforate, impressed, with all the stride more 

 strongly developed and thickly converging towards it. 



Greatest length of axis one and a quarter inches ; 

 ordinary langth one inch. Diameter of shell two-fifths 

 of an inch. 



Geographical Distkibutiox. Found hitherto in the 

 northern part of Cuba, and in the southern part of the 

 peninsula of Florida. 



Remarks. This species is found plentifully at Key 

 West, where it inhabits low grounds near salt water 

 ponds. It attaches itself to saline plants, a few inches 

 from the soil. At other times it retreats under stones. 

 It is, probably, confined to the vicinity of the ocean. It 

 has also been found on other neighboring keys, and on 

 the main land near Cape Florida. The animal varies 

 much in color ; it is shy when kept in confinement. In 

 winter it forms a membranous epiphragm. 



The general appearance of this shell is cylindrical, 

 with both extremities obtuse. The width of the central 

 whorls is nearly uniform ; the upper only become gra- 

 dually narrower to the apex. The number of whorls is 

 usually about nine, but sometimes twelve ; and the pro- 

 gressive increase of the width of the whorl, in revolving 

 from the apex to the aperture, though regular in each spe- 

 cimen, differs so much in different specimens, that some 

 shells are very short and robust, while others are long 

 VOL. 11. 80 



