524 



NORTH AMERICAN INDEX FOSSILS. 



445. A. COStatum Meek and Worthen. (Fig. 706.) Carbonic. 



Radiating costae present on posterior slope ; concentric lamellae 

 elevated. 



Coal Measures : Illinois, Ohio, Kansas, Missouri, Iowa. 



Fig. 706. Allorisma costaium. (Kan. Pal., VI/II. ) 

 FlG. 707. Allorisma granosum. (Kan. Pal., VI/II.) 



446. A. granosum Shumard. (Fig. 707.) Carbonic and Permic. 



Beaks very prominent, incurved ; a slight sinuosity sometimes 

 present in the base. 



Upper Coal Measures : Kansas, Missouri. Permic of Kansas. 



Fig. 708. Allorisma terminate. (Kan. Pal., VI/II.) 



447. A. terminale Hall. (A. subcuneata Meek and Hayden.) 

 (Fig. 708.) Carbonic and Permic. 



Large. Dorsal and basal margins subparallel. 

 Coal Measures of United States from Pennsylvania to Utah. 



Permic of Kansas. 



CXXI. Sphenotus Hall. 



Entire shell almost cylindrical in shape. Posterior end usually 

 obliquely truncate. Beaks very near anterior end, hinge line long 



