320 NORTH AMERICAN INDEX FOSSILS. 



LXIV. PsEUDOSPH^REXocHus Schmidt. 

 Distinguished from Ceraurus by the following characters : con- 

 vex glabella, tapering anteriorly; lateral furrows usually oblique; 

 posterior lobe large, usually not isolated. Glabella one third or 



Fig. 1632. Ceroums pleurex- 

 anthevius. (After Logan. ) 



Fig. 1633. Crotalocephalus niaga- 

 rensis, cranidium and pygidium, X/^- 

 (After Weller.) 



more the width of the cephalon. Free cheeks larger than fixed 

 cheeks. Eyes very close to glabella. Genal angles usually rounded. 

 Pygidium with eight divergent spines. Ordovicic. 



Fig. 1634. a-c, Piiomera canadensis : a, an entire individual ; b, cephalon separate ; 

 ^, pygidium of larger specimen ; d, Pseudosphcerexochus vulcanus, cephalon, X 2 ; <?, 

 Sph(2rexochHs parvus, side view of cephalon, X 2. (All after Raymond.) 



166. P. vulcanus Billings. (Fig. 1634, rf.) Ordovicic. 



Cephalon bordered by a convex rim. Glabella very large and 

 convex. Surface of test covered with low scattered tubercles. 



Chazy of New York and Newfoundland. 



