1894.] 



NATURAL SCIENCES OF PHIJLADELPHIA. 



123 



Taking the meau measurements of these skulls, horribilis presents 

 the narrowest, with a relative average breadth of . 638 and a molar 

 of .112,— its maximum breadth falling far below that of ameWcamts, 

 from which it differs also in color, size and claw. 



The great frontal concavity, breadth of skull and more than all, • 

 great size of the molar, would appear to remove cimiamomeus very far 

 from americantis, but this comparison will be recurred to after con- 

 sidering the variations of arctos. 



In both of the proportions given, cinnamomeus greatly exceeds the 

 average of arctos, which is breadth .700; molar .107, — in each, how- 

 ever, it falls within the extremes of this unstable species, the greatest 



' Estimated ; the skull being broken. 



