Occasional Papers of the Museum of Zoology 3 



Carychium cxiguum Say. 



In the examination of large series of this species two rather 

 distinct forms were noted. The smaller is narrow, glistening, 

 and is probably often mistaken for exile because of its small 

 size, and because of the striations which often become quite 

 regular just back of the aperture. Clapp writes that "there 

 is one character which at once distinguishes exigmim from 

 exile — that is, the swollen body whorl, giving to cxiguum a 

 'bellied' appearance when viewed from the side.'' Besides this, 

 however, the lamellae as seen through the shell of fresh speci- 

 mens will conclusively distinguish it from exile. The lamellae 

 may be described as follows : upper fold small in proportion 

 to the diameter of the last whorl, somewhat sinuate, but never 

 deflected sharply downward. Lower fold evenly sinuate, in 

 well-developed specimens shelf-like for a short distance 

 beneath the upper fold in the last whorl of the shell. The 

 larger form of exiguum is more distinctly "bellied" and the 

 striation, when it occurs, is very indistinct and irregular. 



Carychium exile H. C. Lea. 



The upper columellar fold is very large in proportion to the 

 diameter of the last whorl, almost touching the wall of the 

 whorl at the upper angle of the aperture. Typically it is bent 

 sharply downward at its widest part, the edge turning toward 

 the columella. The lower fold is leaf-like, curling at its edge, 

 wider than in exiguum, and conspicuously projecting from the 

 columella beneath the upper fold. Both lamellae are more 

 persistent in the penultimate whorl than is the case in cxiguum. 

 becoming wider in that whorl before disappearing in the upper 

 whorls. 



The distinct differences in shape and size that these lamellae 

 show should serve to distinguish exile from cxiguum, in case 



