HELIX. 243 



Greatest transverse diameter more than one-fifth of an 

 inch. 



GEOGRAPHICAL DISTRIBUTION. Inhabits the Northern, 

 North-eastern, Middle, and Western States, and is proba- 

 bly a wide-spread species. 



KEMARKS. This shell is found in the same situations 

 as Helix arborea, Say, and resembles it very much, par- 

 ticularly on its upper surface. It may be distinguished 

 from it by the outer whorl, which is more spread towards 

 the aperture ; by the impressed, radiating lines, and by 

 the want of an open umbilicus. The whorls, in this spe- 

 cies, usually revolve in such a manner as to leave no 

 opening between them ; but there is an occasional speci- 

 men with a well-formed umbilicus. 



71. HELIX CHERSINA. 



PLATE XVII. FIGURE 4. 



H. testa minima, conoidea, nitida, tenuissima, pellucida, 

 imperforata ; apertura transversa ; labro simplici, acuto ; 

 basi convexo. 



SYNONYMS AND REFERENCES. 



Helix ckersina, SAY, Journ. Acad. II. 156. 



Exped. St. Peters, II. 258. 



BINNEY, Boston Journ. Nat. Hist. III. 416, pi. 26. f. 2. 

 GOULD, Invertebrata, 185, f. 105. 



ADAMS, Vermont Mollusca, 12; Sillim. Journ. XL. 273. 

 DE KAY, Nat. Hist. New York, 44, pi. 35, f. 338. 



DESCRIPTION. 



ANIMAL bluish-black upon the head, neck, and tenta- 



