TRILOBIT A—PROP ARIA. 



315 



153. C. senaria Conrad. (Fig. 1624, c, t/.) Ordovicic. 

 Anterior extension of cephalon narrowed and shovel-shaped, 



not abruptly concave. Pleural segments of pygidium grooved. 

 Trenton of New York, New Jersey, Ohio, Minnesota, etc. 



154. C. callicephala Green. (Fig. 1624, &.) Ordovicic. 

 Differs from C. senaria in the broad and abruptly concave, 



anterior extension of the cephalon, in the absence of genal spines 

 and in the absence of grooving upon the pleural segments of the 

 pygidium. 



Trenton-Lorraine of New York, Virginia, Ohio, Indiana, Min- 

 nesota, etc. 



155. C. vogdesi Foerste. Siluric. 

 Anterior border of head very broad and flat, much like C. 



niagarensis. Pygidium semicircular anteriorly, and almost straight 



Fig. 1627. 

 Hall.) 



Encrinurus ornatus. (After 



P'iG. 1628. Calyfuene niagaren- 

 is. (After Hall.) 



along the posterior margin. Length of a cephalon 15 mm.; width 

 of glabella including posterior lobes 11.7 mm., at frontal lobe 6.5 

 mm. Length of pygidium 7-17 mm. ; breadth 13-27 mm. 



Clinton of New York, Ohio, Georgia, Tennessee and Alabama. 



156. C. rostrata Vogdes. ' Siluric. 

 Cephalon with a distinct projecting process in front of the gla- 

 bella. The facial sutures cut the anterior border at the apex, 

 giving to the anterior part of the cranidium a triangular form ; at 

 their junction the marginal border is raised and forms a triangular 

 process which supports the projection. 



Clinton of New York and Georgia. 



157. C. niagarensis Hall. (Fig. 1628.) Siluric. 

 Genal angles rounded. Glabella strongly convex, elevated above 



