196 HUMAN FOSSILS. m 



But if a series of sections of mammalian skulls, 

 intermediate between a Eodent and a Man (Fig. 

 29), be examined, it will be found that in the 

 higher crania the basicranial axis becomes shorter 

 relatively to the cerebral length; that the " olfac- 

 tory angle" and "occipital angle" become more 

 obtuse; and that the " craniofacial angle," be- 

 comes more acute by the bending down, as it were, 

 of the facial axis upon the cranial axis. At the 

 same time, the roof of the cranium becomes more 

 and more arched, to allow of the increasing height 

 of the cerebral hemispheres, which is eminently 

 characteristic of man, as well as of that backward 

 extension, beyond the cerebellum, which reaches 

 its maximum in the South American Monkeys. 

 So that, at last, in the human skull (Fig. 30), the 

 cerebral length is between twice and thrice as 

 great as the length of the basicranial axis; the ol- 

 factory plane is 20° or 30° on the under side of 

 that axis; the occipital angle, instead of being less 

 than 90°, is as much as 150° or 160°; the cranio- 

 facial angle may be 90° or less, and the vertical 

 height of the skull may have a large proportion to 

 its length. 



It will be obvious, from an inspection of the 

 diagrams, that the basicranial axis is, in the 

 ascending series of Mammalia, a relatively fixed 

 line, on which the bones of the sides and roof of the 

 cranial cavity, and of the face, may be said to re- 

 volve downwards and forwards or backwards, ac- 



