172 



FOSSIL KEMAJXS OF MAN. 



In such a mammal as a Beaver (Fig. 29), a line (a. b.) 

 drawn through the bones, termed basioccipital, basisphe- 



Deaver. 



FIG. 29. Longitudinal and vertical sections of the skulls of a Beaver 

 (Castor Canadensis), a Lemur (L. Catta), and a Baboon (Cynocephalus 

 Papio), a b, the basicranial axis ; b c, the occipital plane ; t T, the tentorial 

 plane ; a d, the olfactory plane ; / <, the basifacial axis ; c b a, occipital 

 angle ; T i a, tentorial angle ; d a b, olfactory angle ; e f b, cranio-facial 

 angle; g A, extreme length of the cavity which lodges the cerebral hemi- 

 spheres or ' cerebral length.' The length of the basicranial axis as to this 

 length, or, in other words, the proportional length of the line g h to that of 

 a b taken as 100, in the three skulls, is as follows : Beaver 70 to 100 ; Le- 



