FOSSIL REMAINS OF MAN. 173 



noid, and presplienoid, is very long in proportion to the 

 extreme length of the cavity which contains the cerebral 

 hemispheres {(j. h.). The plane of the occipital foramen 

 {b. c.) forms a slightly acute angle with this ' basicranial 

 axis,' while the plane of the tentorium {i. T.) is inclined 

 at rather more than 90° to the ' basicranial axis ' ; and so 

 is the plane of the perforated plate (a. d.\ by which the 

 filaments of the olfactory nerve leave the skull. Again, 

 a line drawn through the axis of the face, between the 

 bones called ethmoid and vomer — the '* basifacial axis " 

 {f. e.) forms an exceedingly obtuse angle, where, when 

 produced, it cuts the ' basicranial axis.' 



If the angle made by the line h. c. with a. h., be called 

 the ' occipital angle,' and the angle made by the line a. d. 

 with a. h. be termed the ' olfactory angle,' and that made 

 by i. T, with a. h. the ' tentorial angle,' then all these, in 

 the mammal in question, are nearly right angles, varying 

 between 80° and 110°. The angle e.f. 5., or that made 

 by the cranial with the facial- axis, and which may be 

 termed the ' cranio-facial angle,' is extremely obtuse, 

 amounting, in the case of the Beaver, to at least 150°. 



But if a series of sections of mammalian skulls, inter- 

 mediate beween a Bodent and a Man (Fig. 29), be exam- 

 ined, it will be found that in the higher crania the basi- 

 cranial axis becomes shorter relatively to the cerebral 

 length ; that the ' olfactory angle ' and ' occipital angle ' 

 become more obtuse ; and that the ' cranio-facial angle,' 



mur 119 to 100; Baboon 144 to 100. In an adult male Gorilla the cerebral 

 length is as 170 to the basicranial axis taken as 100, in the Negro (fig. 30) as 

 236 to 100. In the Constantinople skull (fig. 30) as 266 to 100. The cranial 

 difference between the highest Ape's skull and the lowest Man's is therefore 

 very strikingly brought out by these measurements. 



In the diagram of the Baboon's skull the dotted lines <P(P^ &c. give the 

 angles of the Lemur's and Beaver's skull, as laid down upon the basicranial 

 axis of the Baboon. The line a h has the same length in each diagram. 



