OP coNcnoLOQY. 255 



2. Mesomphix ligera, Say. 



Plate 4, figure 34. 

 Subgloboso, elevated, obtusa, yellowish horn color, translu- 

 cent, shining, whorls 6 — 7, closely striated ; aperture obliquely 

 narrowly semilunar, shell thickened within at the base ; um- 

 bilicus narrow, sometimes closed. 



Diam. 12—15 mill. 



All the Middle and Western States. 

 See the distinctive characters under H. inlerkxtx. 



3. Mesomphix demissa, Binney. 



Plate 4, figure 35. 

 Depressed convex, Avhorls 6, shining, yellowish horn-color, 

 thickly, but not coarsely, striate, base ratlier lluttcned, umbil- 

 icus very small ; aperture very oblique, ahnost transversely 

 compressed-lunate, base of shell thickened within. 



Diam. 10—12 mill. 



Western Pennsylvania ; fossil in Alabama and Texas. 



Much more depressed, more solid, and usually smaller than 

 H. ligera. 



b. Diam.==6 — 7 7nill. 

 4. Mesomphix cerinoidea, Anthony. 



Plate 4, figure 3G. 

 Sub globose, whorls 6, shining, yellowish horn-color, almost 

 smooth, convex below, umbilicus very narrow ; aperture semi- 

 lunar, somewhat oblique, base of shell slightly thickened within. 



Diam. G— 7 mill. 



North Carolina. 



Smoother and more depressed, but otherwise a miniature 

 edition of J/, li'jdra. 



