12 NORTH AMERICAN INDEX FOSSILS. 



30. T. spiculus Hall. Devonic. 

 Differs from the preceding in its thicker annulations, which are 



more strongly rounded, and often appear oblique, and in the 

 fewer and coarser intervening striae. 



Chemung of New York and Pennsylvania. 



Family Conularid^ Walcott. 



X. CoNULARiA Miller. 



Shell elongated pyramidal, with the transverse section varying 

 from quadrangular to octagonal. Each lateral face marked by a 

 median longitudinal groove. Surface transversely striated or 

 ribbed. Posterior (apical) portion of shell divided off by septa. 

 Aperture constricted by four lobes incurved from the margin. 

 Ordovicic-Jurassic. 



31. C. niagarensis Hall. (Fig. 1223.) Siluric. 



Fig. 1223. Conularia niagarensis^ with enlargement of surface. (^ After Hall.) 



Broadly pyramidal, tapering abruptly. Central depression of 

 faces scarcely defined. Striae granulate. 

 Rochester shale of New York. 



