INVERTEBRATES. 143 



Height 7 1H inch; greatest breadth 13 / 16 inch; breadth of the 

 aperture 6 / 16 inch. 



Position and locality: Upper beds of the Keokuk limestone, 

 Warsaw. 111. 



Collector, A. H. Worthen. 



No. 2599 of the Illinois State Museum. 



GENUS MACROCHEILUS. Phillips. 

 MACROCHEILUS ALTONENSIS. (sp. nov.) 



PL XXIV. Figs. l-'a. 



Shell of medium size, subfusiform, symmetrically conical 

 above the last volution. 



Volutions about six. moderately ventricose. the last one about 

 equal to the length of the spire above. Suture well denned. 

 Aperture elongate ovate; surface markings unkown. 



The specimen is a cast in limestone, but clearly shows the 

 characteristics of the genus. 



Length 1% inches; length of the last volution 1 inch; breadth 

 of the same % inch ; length of aperture % inch ; greatest breadth 

 of the same % inch. 



Position and locality : St. Louis limestone, Alton. Illinois. 



Collector. A. H. Worthen. 



No. 2598 of the Illinois State Museum. 



GENUS BELLEROPHON, Montfort. 

 BELLEROPHON GIGANTEUS. Worthen. 



PI. XXV, Figs. 5-oa. 



Bellerophon giganteus Worthen, March, 1884. Bulletin No. 2 of the Illinois State 

 Museum of Natural History, page 8. 



Shell very large, sub-globose: volutions expanding rapidly, 

 rounded over the dorsum and sides ; umbilical region deeply ex- 

 cavated. Aperture reniform or sublunate, mesial band not 

 shown on the cast. Fragments of the shell adhering show that 

 it was comparatively thick. 



