INVERTEBRATES. 137 



Position and locality : Burlington limestone, Montezuma, Pike 

 county, Illinois. 

 Collector. A. H. Worthen. 

 No. 2487 of the Illinois State Museum. 



PLEUROTOMARIA ADAMSI. Worthen. 



PL XXm, Figs. 5-5a. 



Pleurotomaria adamsi, Worthen. March, 1884. Bulletin No. 2, of the Illinois State 

 Museum of Natural History, page 5. 



Shell small, trochiform, conical; length a little more than the 

 diameter of the lower volution. Volutions about six, the last 

 one flat and smooth below the spiral band, umbilical region 

 concave: spiral band prominent, deeply groved, and occupying 

 the angle on the periphery of the lower volution, becoming 

 shallower and less prominent on those above. The elevations 

 defining the upper and lower margins of the spiral band are 

 marked by one or two revolving lines visible with an ordinary 

 glass, which continue on the succeeding volutions where the 

 spiral band becomes obsolete. 



Length 5 16 inch ; diameter of the last volution 4 / 16 inch; spiral 

 angle about 60. 



Named in honor of Mr. W. H. Adams of Peoria county, from 

 whom some of the specimens were obtained. 



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



Collector. W. H. Adams. 



No. 2536 of the Illinois State Museum. 



PLEUROTOMARIA NAVVOOENSIS. Worthen. 



PL XXV, Fig. 3. 



Pleurotomaria nauoooensis, Worthen, March, 1884. Bulletin No. 2, of the Illinois State 

 Museum of Natural History, page 5. 



This form is represented in the State collection by a single 

 cast in limestone from the upper part of the Keokuk limestone 

 at Navoo. 



Shell above the medium size, consisting of about four obliquely 

 flattened volutions, the lower one forming about half the entire 

 length. The periphery of the lower volution shows a flattened 

 space about a quarter of an inch in width that was probably 

 occupied by a spiral band. Form of aperture and surface mark- 

 ings unknown. 

 17 



