COLIMACEA. MOLLUSCA. HELIX. 185 



raised line or tooth, which appears to revolve within the shell 

 parallel to the suture, and sometimes a second nearer to the base, 

 less conspicuous, and terminating farther within the aperture ; 

 beneath flat, umbilical region impressed, and the umbilicus minute. 

 Greatest diameter one tenth of an inch, height nearly as much. 



Animal has the head slate-colored above, the tentacula quite 

 dark ; foot white as printing paper, linear ; space between the 

 four tentacula and neck lighter colored. 



Found in various parts of this State, usually in the fissures of 

 decaying wood, or under fragments of wood in moist places, or 

 in beds of decaying leaves. It inhabits a wide range of territory, 

 having been found as far distant as Missouri. It is not frequently 

 found, however, on account of its minuteness, and its dusky color. 



It is readily distinguished from other species by the remarkable 

 raised lines revolving within the aperture. Usually, but one of them 

 exists ; but when both are present, their parallel position gives them a 

 close resemblance to the track of a rail-road. The oblique plaiting of 

 the whorls is very conspicuous, and renders the exterior quite beauti- 

 ful. The outer lip in fresh specimens has a rose-colored tint. The 

 shell varies considerably in the elevation of the spire, being sometimes 

 much flattened, and again it has a pointed apex. 



Helix chersina. 



Shell mimite, globose-conic^ pellucid, very smooth and shining ; 

 whorls six, suture deep ; aperture narrow ; lip simple ; umbilicus 

 closed. 



Figure 105. 



State Coll., No. 110. Soc. Cab., No. 2394. 



Helix chersina, Say ; Journ. Acad. jXat. Sc, ii. 156. Binnev ; Bost. Joiirn. Kat. 

 Hist., iii. pi. 24, f. 3. 



Shell minute, sub-globose-conic, thin, pellucid, very smooth 

 and shining, of a smoky horn-color ; whorls separated by a deep 

 suture, and so crowded that they appear much higher than 

 broad, and present an elevated, somewhat turretted spire, with a 

 rounded apex ; they are so smooth that scarcely any traces of 

 the lines of growth are visible ; aperture semi-lunar, narrow, 

 24 



