54 
Height in line with trigeminal nerve (V) 
Breadth at trigeminal nerve 
Breadth just belund the facial nerve (VII) 
Height in line with auditory nerve (VIII) 
Breadth behind auditory nerve 
Posterior height, from lower surface of medulla, in advance of hypoglossal nerve 
Posterior breadth at midheight of medulla 
74 
54 
35 
76 
42 
52 
41 
* Teeth. 
Figure 28 shows the manner in which the teeth follow each 
other in the Hadrosauridse as a group. The number of vertical series in 
the dentary and maxillary magazines varies in the different generic forms 
as also does the number of individual teeth in the vertical series. The 
Figure 28. Illustrating the general type of tooth formation and succession in the Hadrosauridse. 
A, internal view of vertical series of teeth of lower jaw; B, view from above of teeth of lower jaw 
worn down by use; C, diagrammatic representation of teeth of both jaws in cross-section. I natural 
size* 
large number of teeth in each jaw and their manner of implantation render 
the dentition remarkably complicated. As the teeth were evidently worn 
down rapidly a system of continuous replacement was necessary and for 
this purpose many reserve or successional teeth were provided in vertical 
series of from five to eight teeth, each tooth in a series overlapping the 
one which preceded it. The vertical series curved outward in the lower 
