1(34 HELICID^E. 



SYNONYMS AND REFERENCES. 



Helix concava, SAY, Journ. Acad. II. 159, anno 1821. 

 KIRTLAND, Ohio Report, 173. 

 SAGER, Michigan Catalogue, 14. 

 BINNEY, Bost. Jour. Nat. Hist. III. 372, pi. 14. 

 ADAMS, Vermont Mollusca, 9. 



DE KAY, Nat. Hist. New York, p. 33, pi. 2, f. 15, a. b. 

 Helix planorboides, FERUSSAC, Tab. Syst. 45. 



Hist. Nat. des Moll. tab. 82, f. 4. 

 PFEIFFER, Monog. Helic. Viv. I. 200. 



Symbols, II. 37. 

 Circinaria planorboides, Beck, Index, p. 24. 



DESCRIPTION. 



ANIMAL. Upper surface grayish, tentacles bluish, 

 base dirty-white, color reddish-orange, posterior extrem- 

 ity slightly tinged with the same. Tentacles slender, 

 cavities into which they are retracted visible, foot nar- 

 row, twice as long as the diameter of the shell. 



SHELL depressed, very slightly convex on the upper 

 surface ; epidermis whitish horn-color, sometimes with a 

 tinge of green ; whorls five, above flattened, below 

 rounded, finely striate obliquely, the outer whorl spread- 

 ing a little towards the aperture ; suture rather deeply 

 impressed ; umbilicus wide, deep, exhibiting all the volu- 

 tions to the apex ; aperture rounded, somewhat flattened 

 above, its edge frequently tinged with reddish brown ; 

 lip sub-reflected at the base of the shell, simple above, 

 and in some specimens considerably depressed near its 

 junction with the outer whorl ; columella with a thin cal- 

 lus, the edge of which connects the upper and lower 

 extremes of the lip. 



