144 



NORTH AMERICAN INDEX FOSSILS. 



large, round, opening laterally; fenestrules oval on non cellulifer- 

 ous side, which is striated, but appears granular when worn. 

 Rochester shale of New York, Canada, etc. 





Fig. 200, a. Semicoscinium tenuiceps. 

 Clinton ; with enlargements. 



Fig. 200, b. Semicoscinium tenuiceps. 

 Niagara ; enlargements of celluliferous and 

 non-celluliferous faces. 



91. S. planodorsatum Ulrich. (Fig. 201, d.) Devonic. 



Fenestrules very small; carina prominent, with circular aper- 

 tures; reverse side flat, with irregularly oval to circular fenestrules, 

 showing no evidence of branching. 



Hamilton of Falls of the Ohio. 



Fig. 201. a, Phylloporina reticulata, X9!^ Fenestella tenax, obverse and re- 

 verse faces, X 4>2 5 c, F. cestriensis, obverse face, X 4/^ > ** Semicoscinium planodor- 

 satum, obverse side, X l A arid X4^; e , Fenestrapora occidentalis obverse, X 4% \ 

 /, Hemitrypa proutana, non celluliferous and celluliferous faces, the latter with part of 

 superficial network, X A l A '■> £> var - nodulosa, X \ x /z \ /l , Reteporidra perundata, ob- 

 verse face, X4>2- (After Ulrich.) 



