292 



LAND AND FRESH-WATER SHELLS OF N. A. [PART L 



Subgenus VENTRIDENS. 



Shell subperforate or umbilicated, orbicularly convex, diapha- 

 nous honi-color ; glassy, more or less wrinkled ; whirls 5-1 ; 

 aperture lunar, almost always furnished at its base with fold-like 

 denticles not reaching the margin ; peristome simple, acute. 

 Animal with a caudal mucus pore. 



Animal (of Z. supiwes&a) bluish-black, darker on the head, 

 eye-peduncles, and neck ; eye-peduncles long and filiform, ten- 

 tacles short. Length twice the diameter of the 

 shell. On the upper surface of the extremity of 

 the foot is a longitudinal fissure or farrow, from 

 which mucus exudes in great quantities, and which 

 the animal shuts and closes at will. 



The species comprising the group for which 1 

 propose the name Venlridens are distinguished by 

 the caudal mucus pore only from those of the subgenus 

 Gastrodonta. 



Fig. 524. 



Fig. 525. 



Zonites glllaris, Sat. — Shell subperforated, subconical : epiderraig 

 sliiuiiig, pale yellowish horn-color ; spire sometimes tending to a point, at 

 other times obtuse ; whirls seven or eight, very minnte at the apex, in- 

 creasing in diameter regularly and gradually, until they reach 

 the aperture, with strongly marked, curved wrinkles ; suture 

 impressed and distinct ; aperture transverse, not much ex- 

 panded ; peristome simple, thin at its edge, within thii-kened 

 with a white, testaceous deposit ; base flat, indented in the 

 centre, near the aperture yellowish-white and opaque ; um- 

 bilicus small and rounded in young shells, obsolete or dimin- 

 ished to a mere point in older ones ; within the base of the 

 ajierture are one or two lamelliform, elongated, nearly jiarallel 

 tet^th, one near the base, the other more central. Greater 

 diam. 8, height 5 mill. 



Helix gidaris, Say, Journ. Acad. Nat. Sci. Philad. II, 156 



(1822); Binney's ed. 18. — Bixxey, Bo?t. Journ. Nat. 



Hist. 111,408, pi. xi,f. 1 (1840); Terr. Moll. II, 251, pi. xxxvii, f. 3,4. 



— DeKay, N. Y. Moll. 46 (1843).— Ferussac, Hist. pi. li. a, f. 4 (?).— 



Pfeiffer, Mon. Hel. Viv. 1, 183, excl. 3 ; Symbolaa, II, 29, excl. B ; in 



