174 INVERTEBRATA OF MASSACHUSETTS. 



crossed obliquely with numerous fine and regular lines of growth ; 

 aperture contracted, rendered trilobate bj' the presence of two 

 small, pointed teeth on the outer lip ; opposite the middle lobe, 

 placed obliquely on the inner lip, is a thin, somewhat curved, 

 white tooth ; lip broad, white, partiallj^ reflected, with a constric- 

 tion behind It. ; umbilicus not large, deep, and partly covered by 

 the extrenn'ty of the reflected lip. Diameter about half an inch. 



tB.nimal dark-bluish slate-color, deeper on the head, back and 

 tentacula ; foot nearly twice as long as the diameter of the shell. 



This well-marked species is not found near the sea-coast, and 

 but rarely in the forests, at the western part of this State. It in- 

 habits all the Atlantic States, and those north of the Ohio. 



It varies much in size and other respects, in different localities. 

 Specimens from this region have the lip narrow, the teeth small, the 

 aperture but slightly contracted, the spire depressed, and are of a 

 medium size. In Ohio it is larger, in Florida much smaller. 



Dr. Binney regards the H.fallax of Say, as a variety of this species, 

 in which the spire is more elevated, and the parts about the aperture 

 gready developed, so that the aperture is nearly closed by the teeth 

 and the stricture behind the lip ; the upper lip-tooth has often two or 

 three points, and the tooth on the inner lip extends quite to the base of 

 the shell, so as to unite with the extremity of the lip. 



The middle one of the three lobes is smallest, and their oudine reg- 

 ularly arched, so as to resemble somewhat the ace of clubs. 



Helix mo'nodon. 



Shell rather depressed, dusky horn-color, hispid : aperture 

 semilunar: lip white, rejiexed : with a single elongated tooth fixed 

 obliquely to the pillar ; umbilical region excavated. 



Figure 113. 



State Coll., No. 105. Soc. Cab., No. 1054. 



Helix monodon, Rackett ; Lin. Trans., xiii. 42, pi. 8, f. 2. Binney ; Bost. 

 Journ. JVat. Hist., iii. pi. 14, f. 1. 



Shell slightly convex ; whorls five or six, narrow, diminishing 

 very gradually in breadth from the outer whorl to the apex, mark- 

 ed with very fine lines of growth, and covered with a dark russet 



