108 



LAND AND FRESH-WATER SHELLS OF X. A. [PART III 



angularly semioval, entire ; peristome simple, straight or thick- 

 ened, often widely expanded. Xo horny jaw. Lingual mein- 



Fig. 216. 



Lingual dentition of Hdicina orbiculata. — [Troschel.] 



brane with teeth arranged 00, 5, 1, 5, 00. Centrals small, apex 

 broad, reflected; first and second laterals broader, rounded at 

 base, apex recurved, denticulated ; third lateral suboval, apex 

 recurved, denticulated ; fourth lateral long, narrow, irregular 

 shaped, apex recurved, denticulated ; uncini long, narrow, apex 

 recurved, denticulated. 



ScBGExrs OLIGYRA, Say. 



Shell subglobose or conic; spire equalling or excelling the last 

 whirl, whirls ecarinate ; peristome expanded. 



Fig. 21 ; 



Helicina orliicnlata, Say. — Shell subglobose, acute at apex, 

 solid, smooth, very delicately striated ; color yellow- 

 ish, brownish, or ash-colored, with a linear, pale zone 

 at the periphery, which passes up the spire at the 

 suture, and makes it white ; there are also in many 

 specimens numerous capillary zones, and some speci- 

 mens are mottled with pale spots ; whirls five, well 

 rounded, suture well impressed ; aperture rather large, 

 semilunar; peristome white, moderately reflexed. and 

 often greatly thickened and protruded by age ; columella short, joining 



Bdicina orbiculata, 

 enlarged. 



