296 



NORTH AMERICAN INDEX FOSSILS. 



Niagaran of New York, Indiana, Illinois, Wisconsin, Tennessee 

 and Arkansas. 



Fig. 1606. llliznus ioxus. 

 (After Hall.) 



Fig. 1607. Illcsnus ioxus, cephalon and 

 pygidium. (After Hall., 20th Mus. Rep.) 



102. I. insignis Hall. (Fig. 1608.) Siluric. 



Cephalon parabolic in outline, strongly convex; dorsal furrows 



terminate near anterior margin of cephalon in pit-like depressions. 



Eyes two and one half to three times as long as high. Anterior 



Fig. 1608. lllcBnus insignis, a cephalon with free cheeks, restored. 

 (After Hall, 20th Mus. Rep.) 



and lateral margins bent slightly upwards, forming a narrow, lip- 

 like border. Pygidium usually with a slight median longitudinal 

 ridge extending from near the center to the posterior extremities. 

 Niagaran of Ohio, Indiana, Illinois and Wisconsin. : 



