BULLETIN NO. 2. 



GENUS NATICOPSIS, McCoy. 



NATICOPSIS MADISONENSIS. (sp. nOV.) 



Shell large, snb-rliomboidal or sub-rectangular in outline ; volu- 

 tions about three, the last one comprising more than two-thirds 

 the entire length of the shell, all rounded, and the last quite 

 gibbous ; umbilicus deep, aperture apparently subcircular. The 

 specimen is a cast in limestone, and shows no external markings 

 except some faint lines of growth. 



Length 'iy^g inches; breadth of the last volution l-f\ inches. 



In form and size this shell approaches most nearly to N. gi- 

 ganteus of the Coal Measures, but it differs from that in having 

 one less volution, and it also lacks the flattened depression on 

 the outer volution which characterizes that species. 



Position and locality : St. Louis limestone, Madison county, 

 111. 



]So. 254G of the Illinois State collection. 



Collector, A. H. Worthen. 



GENUS POLYPHEMOPSIS, Portlock. 



POLYPHEMOPSIS ? KEOKUK, (sp. nOV.) 



A cast of this shell in limestone from the lower portion of the 

 Keokuk limestone in the vicinity of Keokuk presents the following 

 characters : 



Shell about the medium size, consisting of about five moderately 

 convex volutions, the last one constituting more than one-half the 

 entire length. The volutions taper gradually, and present no indi- 

 cations of external ornamentation. 



Exact form of aperture unknown. Length of the four volutions 

 preserved, 2f inches ; length of last volution, 1| inches ; breadth 

 of the same where it seems to be somewhat flattened by pressure, 

 f inch. 



No. 2194 of the Illinois State collection. 



Collector, Mr. L. A. Cox of Keokuk. 



LAMELLIBRANCHIATA. 

 GENUS SCHIZODUS, King. 



SCHIZODUS MAGNUS, (sp. nOV.) 



Shell large, ovate sub-quadrangular, convex, the greatest con- 

 vexity being about half-way from the beaks to the ventral mar- 

 gin ; anterior extremity comparatively long and broadly rounded, 

 posterior side about once and a half the length of the anterior, 

 obliquely flattened behind the beaks with a well defined umbonal 



