BUPFALO SOCIETY OF NATU^L SCIENCES 



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widest at about its middle, thence gradually narrowing backward to 

 its point of union with the blade portion; in side view rising gently 

 upward toward the anterior extremity, which is formed into a blunt 

 beak. Depth at middle of mandible contained a little over three 

 times in its total length. 



Kopanon, an axe or chopper; gnathos, jaw. Crassus, dense, in 

 allusion to the dense and robust appearance of the element.] 



Remarks. — This mandible has a certain resemblance to both the 

 Dinomylostomid as weU as the Ptyctodont type of mandible; and 

 we have hesitated as to which to refer it. But in view of the fact that 



Fig. 28. Copanognathus crassus, n. g., n. sp. Left Mandible, X | 

 ^, from above; 5, from inner side. Type. £1944. 



the tritoral area is situated in front, and also because of the form of 

 the element as a whole, and of its microscopic structure which shows 

 typical bone cells, it is more suggestive of an Arthrodiran than a 

 Palaeomylid mandible. We are inclined therefore to regard it as an 

 arthrodire and allied to the genus Dinomylo stoma. From this it is 

 easily distinguishable by its straightness fore-and-aft — Dinomylostoma 

 being decidedly sigmoid in cross-section, with the front half of the 

 element convex outward — and by the form of the blade portion, 

 which is relatively deeper near the posterior end. It may also be 

 noted that there is no demarcation between the front and hind 

 halves of the element, as in most species of Dinomylosioma. 



