136 PALAEONTOLOGY OF ILLINOIS. 



and ornamented below the spiral band with nine or ten revolving 

 lines, that decrease in number on the succeeding volutions. 



Spiral band concave and located a little above the middle of 

 the lower volution, and defined by two strong revolving lines, 

 the upper one of which is the strongest. There are also two or 

 three revolving lines within the spiral band, and three or four 

 on the upper angle of the volution, the last one of which is 

 much stronger than the others. 



Length 6 /i 6 inch, diameter of the outer volution about 4 /ie 

 inch; spiral angle about 43. 



This shell is nearly related to P. subconstricta,, Meek and Wor- 

 then, described and figured in Vol. II of these reports, page 351, 

 PI. 28, fig. 6, but differs from that in its surface ornamentation, 

 and especially in its spiral angle. 



Position and locality: Coal Measures, Peoria county, 111. 



Collector, Mr. Gifford. 



No. 2535 of the Illinois State Museum. 



PLEUROTOMARIA MONTEZUMA. Worthen. 



PI. XXIV, Fig. 2. 

 Pleurotomaria montezumn, Worthen, 1883. Geol. Surv. of Illinois, Vol. VII, page 324. 



This fine shell is only known from an imperfect cast of the 

 last volution. 



Shell attaining a large size, broadly conical in outline ; whorls 

 three or more, diminishing rapidly in size tow r ards the apex. 

 Last whorl obliquely flattened, showing a lateral surface about 

 two inches in breadth. This is traversed by about eight rather 

 strong revolving striae, separated by shallow depressions that 

 are about % of an inch wide near the aperture. The under side 

 of this volution was also traversed by revolving striae about 

 half as widely separated as those on the side of the volution, 

 but their number cannot be accurately determined from the im- 

 perfect state of preservation of the only individual yet obtained. 

 A raised line around the inner side of the volution, indicates the 

 presence of a rather wide and deep umbilicus. 



Greatest diameter of the last volution, 4% inches; height of 

 the volution 1% inches. 



