30 NEW-YORK FAUNA — MOLLUSCA. 



Helix arborea. 



PLATE II. FIG. 10. a. B. c — (STATE COLLECTION.) 



Helix arborea. Say, Nich. Ency. Vol. 4, pi. 4, fig. 4. 



H. id. Binney, Bost. Jour. Nat. Hist. Vol. 3, pi. 26, fig. 1. 



H. id. Gould, Invertebrata of Mass. p. 182, fig. 110. 



H. id. Adams, Am. Journal Science, Vol. 40, p. 273. 



H. id. Wheatley, Catalogue of Shells of U. S. No. 494, p. 19. 



Description. Shell small, thin, fragile, orbicular, pellucid, depressed, very little elevated ; 

 concave beneath. Whorls four to five, slightly rounded above, with a distinct suture, and 

 minutely wrinkled irregularly in the direction of the lines of growth ; beneath smooth, with 

 a wide and deep umbilicus. Aperture sublunated. Lip simple, thin and brittle, its junction 

 with the body-whorl acute. 



Color. Corneous, occasionally deep brown and even blackish. Animal with a dusky head 

 and neck, lighter behind. 



Diameter, ■ 2. Height, 0-13. 



The species has a wide geographical range. It has been observed at Troy in this State by 

 Dr. Newcomb, and at Staten island in Rockland county. According to Dr. Gould, it may 

 be confounded with H. cellaria, indentata, gularis and electrina. It is smaller than the first ; 

 has not the distant impressed radiating lines of the second, nor the peculiar tooth within the 

 aperture of the third, and is distinguished from electrina by its greater number of whorls and 

 less polished appearance. 



Helix electrina. 



H. electrina. Gould, Invertebrata of Mass. p. 183, fig. 111. 

 H. id. Adams, Am. Journ. Science, Vol. 40, p. 273. 



Desertion. Shell small, orbicular, depressed, conical, pellucid, fragile, and the lowest 

 whorl suddenly enlarging as in H. indentata. Whorls four, conspicuously wrinkled by the 

 lines of growth. Lip moderately thick and shining ; its outline nearly a direct section of the 

 whorl. Umbilicus moderate, smaller than in the preceding. Aperture rounded. Color, 

 amber. 



Diameter, 0-2. Height, 0-13. 



Dr. Gould, to whom we are indebted for this species, speaks of it as resembling indentata 

 above and arborea beneath. It is certainly very closely allied to both. It has been noticed 

 in Massachusetts and Missouri. I have not seen it, but Dr. Newcomb has found it near Lake 

 George in this State. 



