op coNCHOLoay. 255 



2. Mesomphix ligera, Say. 



Plate 4, figure 34. 



Subglobose, elevated, obtuse, 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 //. inlertcxta. 



3. Mesomphix demissa, Binney. 



Plate 4, figure 35. 



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

 thickly, but not coarsely, striate, base rather flattened, umbil- 

 icus very small ; aperture very oblique, almost 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.=Q — 7 mill. 

 4. Mesomphix cerinoidea, Anthony. 



Plate 4, figure 36. 



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. 6 — 7 mill. 



North Carolina. 



Smoother and more depressed, but otherwise a miniature 

 edition of M. ligera. 



