FAUNA AMERICANA. 127 



of the full grown Canadian beaver : (the extremi- 

 ty of the snout of the Osieopera, together with 

 the upper incisors, have been destroyed.) 



Total length of the skull, - 



Length of the frontal bone, 



Breadth of do . 



Length of the parietal bone. 



Breadth of do. 



Length of the zygomatic arch, - 



Breadth of do. 



Width across from one zygoma to the other. 



Breadth of the palate bones between the molars, 



Length of the zygomatic fossa, - 



Breadth of do. 



Length of the lower jaw not including the incisors, 4 



Breadth of the same including the molars. 



From the top of the coronoid process to the base 



of the jaw, - - - 12 2 4 



Description. Frontal bone nearly double the 

 length and breadth of that of the common beaver, 

 flat and scabrous, forming on each side a similu- 

 nar ridge, projecting into the orbits ; orbit of the 

 eye small, and nearly circular, which is due, prin- 

 cipally, to the extraordinary development of the 

 zygomatic processes of the temporal and jugal 

 bones, which are produced downward and back- 

 ward, so as to conceal the posterior half of the 

 lower jaw, together with the teeth, anteriorly 

 arched, scabrous, and ventricose ; the jugal por- 

 tions being developed anteriorly and inferiorly so 

 as to form on each side a bofiy antrum, or cavit}^, 

 capable of containing in all two or three ounces 



