184 CERION, GROUP II. 



Varies in degree of elongation, and in the form, which may be 

 either cylindrical or more or less tapering from the last whorl up- 

 wards. Rarely the riblets are very weak and irregularly developed. 

 Maynard states that the ribs of the last whorl vary from 16 to '20 in 

 number. 



O. nanus occurs, according to Maynard, " in a' space which \& 

 only five or six yards wide by twenty long, on this little key, and as 

 they were rigidly confined to this narrow area, which on a good 

 sized chart of the West Indies would be more than covered by the 

 point of a fine cambric needle, I consider that this species has the 

 most restricted range of any animal with which I am acquainted. 

 This spot is on the west end of Little Cayman, on the easternmost 

 of the two paths that cross the key, near their junction. 



" In habit, this species is social, and 1 found many of them cling- 

 ing to a kind of heath-like plant which was about eighteen inches 

 high, and which had small grey leaves of nearly the same color as 

 the shells, and which on being crushed, gave out a strong odor. 

 Here these Strophias were exposed to the burning rays of a nearly 

 vertical sun, and the heat in which they lived during the day was 

 intense. Some, perhaps one-third of them, had retreated beneath 

 stones, a situation in which it is rare to find a Strophia, the only 

 other species that I have found in a similar situation, being S. incana 

 from Key West, which retreated from the cold of winter, and one 

 other species occurring in the pine wood on the island of New 

 Providence, to be mentioned later. It is evident that in this species,, 

 we have a Strophia dwarfed to an extreme degree, from feeding on 

 the pungent leaves of the plant described, and isolated as it is by 

 surrounding areas of rough, jagged rocks, the process of diminution 

 has gone as far as it can go and allow the animal to live as a 

 Strophia, with the ordinary habits of Strophia. The ground was- 

 strewed with thousands of dead shells, showing that mortality among 

 them was great." (Maynard.) 



C. PANNOSUM (Maynard). PL 27, figs. 4, 5, 6. 



Shell perforate and shortly rimate, oblong or subcylindric, solid 

 and strong; white, or sometimes bluish or fleshy white, uniform or 

 faintly flecked with flesh color above. Whorls about 11, slightly 

 convex, the last three of about equal diameter, or the penultimate 

 may be wider; those earlier forming a straight-sided cone. Last 



