252 HELICID^. 



mens, being one-fourth of an inch in diameter, and difier 

 from them in having the umbilicus entirely closed. They 

 have seven full whorls, which are beautifully fine and 

 distinct to the very nucleus, which is uncommonly small. 

 I consider the umbilicated shells to be immature, or not 

 fuUy developed ; though an examination of a larger num- 

 ber may show that the full-grown shell is also umbilicated. 



The present species resembles some varieties of Helix 

 ligera, Say, in form and general appearance, although 

 its size is much less. This remark, which was made by 

 Say, in his original description, is entirely inapplicable 

 to the specimens which are usually known as Helix 

 gularis. It also resembles Helix suppressa, Say, the 

 next described species, with which it has long been con- 

 founded. But it has at least one more whorl ; the spire 

 is much higher ; the nucleus of the shell is smaller, 

 so that the first two whorls are finer and more deli- 

 cate ; and the base is not so convex. The base of the 

 shell is exceedingly like that of Helix interna. 



It is the totality of the characters which makes up the 

 species ; for individuals differ considerably in the height 

 of the spire, the size of the umbilicus, and in the degree 

 of prominence of the teeth. One tooth is often wanting. 



The deposition of testaceous matter, thickenmg the 

 shell at its aperture, occupies about one-fourth of the 

 base, through which it is seen. The character of the 

 lamellar folds, within the aperture, resembles those of 

 Helix epistylium, Miiller, in which species they are large 

 and prominent, although usually overlooked in the de- 

 scriptions. 



