118 



Cells. 



VERTICAL SECTION OE THE MASTODON HEAD.* 



(Elate XVII.) 



This head (the base of which is represented in Plate IV.) is a very perfect 

 one, and appears to have belonged to an animal ten or twelve years old. 

 The two small milk teeth, the third or three-ridged, are in place, and also 

 the first permanent molar, a little worn. 



• 



The whole head measures in length 28 inches. 



The whole head measures in height 16 „ 



The whole head measures, at the vertex, in breadth 15 „ 



A vertical section, a little to the left of the median line, exhibits on 

 the right side, the vomer ; on the left, the nasal cavity fully exposed. The 

 Diploic first appearance that strikes us is the vast number and extent of the diploic 

 cells ; for they occupy two-thirds of the surface of the crania] section. 

 Above, behind, and, in part, below, they 'surround the cerebral cavity. The 

 outer table of the bone which encloses them is about the eighth of an inch 

 in thickness ; the inner is rather more. The space between the two tables, 

 at its broadest part, is seven inches : this space gradually diminishes from 

 the vertex backwards and downwards to the foramen magnum. 



* For permission to make this vertical section, I am under obligations to President Sparks, and to 

 Professors Agassiz and Wyman, of the University at Cambridge. 



