134 GASTEROPODS. 



verse to the axis of the shell, forming well-defined annula- 

 tions, as in D. annulostriatum Meek & Worthen. The second 

 has the costse much less prominent, and arranged obliquely or 

 spirally, as in the species under consideration. A third type 

 has the ridges running longitudinally, as is rather imperfectly 

 shown in D. sublceve Hall ; and as is well seen in the type of 

 the genus D. elephantinum Linnaeus. The fourth variety has a 

 perfectly smooth surface, as in D. venustum Meek & Worthen. 



Pleurotomaria sedaliensis MILLER. 

 Pleurotomaria sedaliensis Miller, 1891: Geol. Sur. Indiana, 17th Ann. Rep,, 



Adv. sheets, p. 83, pi. xiv, fig. 13. 



Horizon and localities. Lower Carboniferous, Kinderhook 

 limestone : Sedalia. 



Pleurotomaria lens (HALL). 

 Euomphalus lens Hall, 1860: 13th Ann. Reg. Rep. Univ. New York, p. 



109. 

 StraparoUus lens Meek & Worthen, 1S66 : Geol. Sur. Illinois, vol. El, p. 



159, pi. xiv. figs. 7a-b. 



Shell of medium size, lenticular, like P. illinoiensis in general 

 shape, but with the spire slightly more elevated, Volutions 

 about four in number, the last sharply rounded around the 

 periphery ; convex below. 



Horizon and localities. Lower Carboniferous, Chouteau 

 (Kinderhook) limestone : Moniteau county. 



Pleurotomaria montezuma WORTHEN 



Pleurotomaria montezuma Worthen, 1883 : Geol. Sur. Illinois, vol. VII, 



p. 324. 

 Pleurotomaria montezuma Worthen, 1891: Geol. Sur. Illinois, vol. VIII, 



p. 138, pi. xxiv, fig. 2. 



Shell very large, turbinate ; apical portions considerably 

 elevated. Volutions about four in number, rapidly increasing 

 in size toward the aperture ; the upper ones strongly convex, 

 the last more or less flattened above and below, forming a 

 rather well-marked angularity around the periphery. Aperture 

 obliquely ovate. Surface ornamented by prominent, revolving 

 carinae, of which seven or eight traverse the whorls above the 



