182 INVERTEBRATA OF MASSACHUSETTS. 



FIGURE 109. 

 State Coll., No. 106. Soc. Cab., No. 1058. 



Helix indentata, SAY; Journ. JLcad. Nat. Sc., ii. 372. BINNEY; Bost. Journ. 

 Nat. Hist., iii. pi. 29, f. 1. 



Shell small, orbicular, very low conical, thin, pellucid, very 

 light horn-color, highly polished and shining ; whorls four, slight- 

 ly convex, the whole spire having a conical slope from the apex 

 to the edge ; the outer one rapidly increasing, marked with some- 

 what remote, sub-equidistant impressed lines, in the direction of 

 the lines of growth, the intervening spaces very smooth ; suture 

 moderately deep ; aperture large, well rounded ; lip simple ; base 

 having the umbilical region deeply excavated, but not perforated, 

 with very few exceptions, the lip usually terminating at the cen- 

 tral point. Diameter one fifth of an inch, sometimes more. 



Animal bluish-black upon the upper parts ; margin and pos- 

 terior extremity lighter. 



Found in company with H. arborea and H. striatella, about 

 decaying stumps and logs. At Oak Island, in Chelsea, I have 

 found it abundantly. It has been noticed in New Jersey, Penn- 

 sylvania, and Ohio. 



This species is of about the same size as H. arborea. Its color is 

 much lighter, its apex less depressed, its whorls less in number by 

 one, the outer whorl increases much more rapidly, its umbilicus is 

 usually closed ; and, moreover, the impressed lines, which look like 

 water lines, or the lines on a gooseberry, apparently radiating from 

 the umbilicus, are entirely characteristic, and distinguish it from every 

 other species. They are not readily discerned without a magnifier. 



HELIX ARBOREA. 



Shell small, orbicular, depressed, thin, pellucid, shining ; 

 brownish horn-colored ; whorls four, minutely wrinkled ; aperture 

 rounded ; lip simple ; umbilicus open. 



FIGURE 110. 



State Coll., No. 96. Soc. Cab., No. 1057. 



Helix arborea, SAY ; Nicholson's Encyc., (Amer. ed.), iv. pi. 4, f. 4. FERUSSAC ; 

 Hist. Nat. des Moll., No, 219. BINNEY ; Bost. Journ. Nat. Hist., iii. pi. 26, f. 1. 



