230 



LAND AND FRESH- WATER SHELLS OF N. A. [PART L 



in this particular, from most of land shells, and especially from 

 the Helices, which always, so far as I know, retain their original 

 attachment to the apex of the shell. It has been thought that 

 the breaking of the spire, after being left by the animal, and 

 becoming dry and brittle, is accidental ; but I conceive that the 

 effect is much too constant to be accounted for in that way. I 

 have never been able to find a mature specimen with the apex. 

 And in all the various countries which it inhabits, including the 

 whole southern part of Europe, the northern part of Africa, the 

 islands of the Mediterranean, the Canaries, Madeira, &c., the same 

 peculiarity attends it. If it were only an accident, some few in 

 this wide extent might escape. I doubt not, therefore, that it is 

 effected by the action of the animal itself. It may be that the 

 calcareous matter of the shell is absorbed at the point of division, 

 previous to the formation of the new septum. 



Mr. Say made out his description from an imma 

 ture specimen. 



Moquin-Tandon describes the Jaw as low, some- 

 what curved from front backwards, of a tawny 

 orange color, extremities attenuated, generally 

 somewhat pointed ; the concave margin forming an 

 elliptical arch with a slight projection towards the middle ; verti- 

 cal striae very delicate ; marginal denticles scarcely perceptible. 



Fig. 391. 



Subgenus OPEAS, Albers, 



Shell minutely perforated or rimate, thin, striated, slightly or 

 moderately smooth-; whirls 6-8, rather convex, the last usually 

 compressed ; aperture ovate-oblong, equalling one-third to one- 

 fourth of the shell's length ; peristome simple, acute, its colu- 

 mellar margin reflected. Size moderate or small. 



Stenogyra Sllliula; Pfr. — Shell small, elongated, turreted, trans- 

 parent, with delicate, longitudinal striae, sometimes of a spermaceti white, 

 and sometimes wax-yellow ; whirls about eight, convexly rounded, re- 

 volving more closely at apex than elsewhere, so as to form a somewhat 



