OSTEOLOGY OF E. DOLLOVIANUS, COPE 



5 



served. The skull is broken on the mid-line, and the top, which 

 was originally quite flat, has been turned up so that the bones 

 appear in the same plane as the bones of the face. The promi- 

 nent outer process of the pterygoid bone, which abuts against 

 the inner side of the lower jaw, appears at the lower posterior 

 angle of the skull, and to its posterior edge is attached the articu- 

 lar bone of the lower jaw in an inverted position. The lower jaw 



Fig. I. — Anterior portion of the skull ; left side. ^ natural size. 



is distinct from the mass containing the skull, but in the figure is 

 placed in the correct position. 



Noticeable is the large size of the orbit, with its prominent 

 border all around, and its elevated position at the posterior angle 

 of the skull. There is but a single large canine tooth in the 

 upper jaw where Dimetrodon has two, but this is, perhaps, of no 

 great taxonomic value, as in forms with successional teeth it 

 is very possible that one may be lost before the other is far 

 enough developed to appear. Neglecting this difference, the 

 number of teeth in the upper jaw is the same (seventeen) in both 

 genera. In Fig. 2 is shown a restoration of the skull of the 

 Pelycosauna^^\x\:)X\'=>\\.&6. in 1899 (i). A comparison with Fig. i will 

 show that this restoration is in all essentials correct, at least as 

 regards the side and top. Such structures of the base of the 



