140 GASTEROPODS. 



glass. A series of small transverse folds or wrinkles is quite 

 conspicuous toward the inner margin of the outer whorl; each 

 fold appears to originate at a distinct node, and extends about 

 one-half to two-thirds the distance to the periphery. 



Horizon and localities. Upper Carboniferous, Coal Meas- 

 ures: Clinton (Henry county). Knob Noster (Johnson 

 county), Kansas City. 



The species under consideration is widely distributed 

 through the Lower Coal Measures of the continental interior, 

 having been first recognized in 1857, by Cox, who figured it as 

 Pleurotomaria depressa. This term had been used, however, 

 previously. Nothing more was heard of the shell for more than 

 thirty years, when it was found in the vicinity of Des Moines, 

 Iowa, and renamed P. modesta, inasmuch as Cox's name had been 

 pre-occupied. Two years later, Miller rechristened the form 

 Pleurotomaria Kentucky ensis. In the meanwhile Worth en re- 

 ported a shell from Mercer county, Illinois, under the name of P. 

 illinoisensis, giving at the same time a very meager description 

 and no figures. Finally, in 1891 the eighth volume of the Illi- 

 nois survey appeared, in which was given a figure of Worthen's 

 shell, leaving but little doubt that it is identical with the form 

 first noted by Cox. 



Pleurotomaria perhumerosa MEEK. 



Plate xlviii, fig 5. 

 Pleurotomaria perhumerosa Week, 1872: U. S. Geol. Sur. Nebraska, p. 232. 



pi. iv, figs. 13a-b. 



Shell of medium size ; volutions four to six in number, 

 expanding moderately from the apex; the body whorl some- 

 what produced below; all the turns with a pronounced revolv- 

 ing angularity, above which is a rather broad, flattened area 

 sloping outward and downward from the suture. Suture well 

 marked. Aperture rather large, oval, with two angularities 

 above. Surface glabrate, with fine lines of growth, and often 

 a few low, rounded elevations running parallel to the angularity 

 near the periphery. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures: Kansas City. 



