312 



NORTH AMERICAN INDEX FOSSILS. 



146. A. hamata (Conrad). (Fig. 1622.) Devonic. 



Median lobe of glabella subrhomboidal, separated from the two 



lateral lobes by a furrow reaching the neck furrow. Median lobe 



rises backward. Neck ring with a tubercle in the middle and pro- 



FlG. 1622, Acidaspis hamata, central portion of head with occipital spines, profile 

 and surface views. (Pal. N. Y., III.) 



jecting behind in two long recurved spines. 



Helderbergian of New York. 

 147. A. tuberculata Conrad. (Fig. 1623.) Devonic. 



Fig. 1623. Acidaspis tuberculata, a nearly complete small individual ; central por- 

 tion of the head; free cheek with eye tubercle. (Pal. N. Y., III.) 



Eye at inner angle of free cheeks. 

 Glabella pustulose. 



Lateral lobes of glabella oval. 

 A single occipital spine present. 



Helderbergian of New York. 

 148. A. callicera Hall and Clarke. Devonic. 



Differs from A. tuberculata in its less depressed and narrower 

 glabella, its weaker marginal spines, its weaker occipital spine, and 

 its almost straight genal spines. 



Onondaga of New York and Ontario. 



LVni. Odontopleura Emmrich. 

 Distinguished from Acidaspis in that the occipital ring is smooth 

 or has merely a central tubercle. Ordovicic. 



