28 NEW-YORK FAUNA — MOLLUSCA. 



Helix tridentata. 



PLATE II. FIG. 7. a. b. — (STATE COLLECTION.) 



Helix tridentata. Say, Nicli. Ency. Am. Ed. Vol. 4, pi. 2, fig. 1. 

 H. id. Feedssac, Hist, des Moll. pi. 51, fig. 3. 

 Helice tridentee. Lamarck, An. sans vert. Ed. Brux. Vol. 3, p. 309. 

 H. id. BiNNET, Bost. Journ. Nat. Hist. Vol. 3, pi. 22, fig. 1. 

 H. id. Gould, Invertebrata of Mass. p. 173. 



Description. Shell depressed, with the spire but little elevated. Whorls five to six, slightly 

 convex, and crossed obliquely by numerous minute elevated lines. Aperture contracted, tri- 

 lobate by three curves on the outer lip, which, at their junction, form two small acute teeth ; 

 a third slightly curved and transverse tooth on the pillar-lip. [Outer lip broad, reflected. 

 Umbilicus large, deep, and partially covered by the reflected outer lip. 



Color. Epidermis brownish horn-color. Animal dark bluish slate ; deeper on the head, 

 back and tentacles. Foot nearly twice as long as the diameter of the shell. 



Diameter, 0' 5 — 0*7. 



This species is found from Massachusetts to Missouri, and along the Atlantic to Florida. 

 It is common in many parts of this State. 



Mr. Binney supposes the H.fallax of Say to belong to this species. The description of 

 fallax shows it indeed to be closely allied to that species, but, as we think, with sufficient 

 distinctive characters. 



Helix fallax. 



PLATE IU. FIG. 23. a. b. — (STATE COLLECTION.) 



Helix fallax. Say, Journ. Acad. Nat. Sc. Vol. 65, p. 119. 

 H. tridentata, var. Bihney, Bost. Jour. Nat. Hist. Vol. 3. 



Description. Spire elevated, convex, often decorticated. Whorls five to six, with elevated 

 lines. Lip reflected, with a deep stricture behind nearly closing the aperture, bidentate. 

 Teeth separated by a profound sinus : upper tooth reflected into the mouth ; lower tooth 

 placed near the base. Pillar-lip with a large subtriangular lamelliform tooth curving down- 

 wards. Umbilicus open, exhibiting all the volutions. 



Color. Epidermis yellowish horn-color ; reflected portion of the lip white. 



D iameter, • 5 . Height, • 3 . 



The chief distinctive characters of this species are to be found in its smaller size, more 

 elevated spire, more contracted aperture, and the peculiar shape of the tooth on the pillar-lip. 

 It is found from New- York to South Carolina. The Carolina specimens, according to Mr. 

 Say, are as large as H. tridentata. 



