CEPHALOPODA— ORTHOCHOANITES. 75 



Fig. 1289. Mitrocei-as gebhardi,h2isa\v\tyf,y^y2,. (After Hall.) 



80. M. gebhardi Hall. (Figs. 1289, 1290.) Siluric. 



Spire moderate apical angle about 60° ; umbilical region sharply 

 angulate ; surface smooth. 



Upper Siluric (Cobleskill and Akron) of New York, etc. 



