Binney on Terrestrial MoUusks. 71 



ficiently strong and constant to warrant the separation, 

 though many intermediate forms occur, scarcely referable 

 to one more than to another. The present form occurs 

 less plentifully in the Southern States, its place being 

 filled by the two others. 



Petiver's No. 6, is this species. Triodopsis lunula is 

 also one of its synonyms. The generic description is 

 given (vol. i. p. 49), — the specific description is as fol- 

 lows : — 



Depressed, mouth narrow with thick lips, umbilicus lunulated. 

 In Kentucky. Forms subgenus Menomphis. 



In Ravenel's Catalogue, p. 9, (1834), a variety of H. 

 tridentata is mentioned under the name of ephebus. I 

 find among Say's manuscript the following description 

 of it : — 



H. TRIDENTATA S. var. ephehus. Small ; labrum much more 

 obtusely rounded ; the elevated lines of the whorls more prominent 

 and obvious. Breadth two fifths of an inch. 



HELIX FALLAX Say vol. ii. p. 183, pi. xxviii. 



Htlix fallax Say, (Binney's ed.) p. 27. 



DeKay, N. Y. Moll. p. 28, pi. iii. fig. 23. 



Chemnitz, 1. c. i. 364, (1846). 



Pfeiffer, 1. c. iii. 263. 



Reeve, Con. Icon. No. 686, (1852). 

 Helix tridentata Binney, Bost. Journ. 1. c. pi. xviii. fig. 3. 



This is certainly more than a variety of tridentata Say. 

 Not only are the characteristic differences well marked, 

 but the habits of the respective animals are different. Mr. 

 J. G. Anthony tells me that tridentata is found on hill- 

 sides in the grass, while fallax inhabits rich soils, in 

 woods, under logs, and is not gregarious like the former. 

 The difficulty is to mark the dividing line between the 

 many varieties of fallax^ some of which are quite as dis- 

 tinct as H. Hopetonensis Shuttl. 



