No. 2300. 



SKELETON OF DIMETRODON GIGAS—GILMORE 



531 



sidered short. This process has been broken off and is missing from 

 specimen No. 8635, U.S.N.M., but is shown restored in its entirety 

 on the right side of the posterior aspect of the skull in figure 1. The 

 upper extremity on the left side was purposely left out so that the 

 artist could depict the decided depression on the posterior border of 

 the squamosal. 



If this articular depression is not for the reception of the upper 

 end of a process from the quadratojugal, I am utterly at loss to 

 know its function. That other specimens have obscurely indicated 

 such an extension of tliis process is shown in a figure ^ of the pos- 

 terior aspect of a Dimetrodon skull illustrated b}^ Case, where the left 

 element is shown extending up as high as the paraoccipital process. 



Fig. 3.— Skull of Dimetrodon gigas Cope, No. 8635, U.S.N.M. Palatal view. One-foueth nat- 



UKAL size, bs, BASISPHENOID; /. St., facet "WITH WHICH THE STAPES ARTICULATED; _;, JUGAL; TOI, MAX- 

 aLARY; OCC. OCCIPITAL CONDYLE; pi., PALATINE; -pmx, PREMAXILLARY; p. OC, PARAOCCIPITAL PROCESS; 

 pt., PTERYGOID; q., QUADRATE; qj., QUADRATOJUGAL. 



The union of the quadratojugal and quadrate on the ventral 

 border is by an inverted V-shaped notch on the distal side of the 

 former which fits over the outward extension of the articular por- 

 tion of the latter. Immediately above this notch on the medial 

 side is the rounded border foiming the outer boundary to the fora- 

 men between these two bones. 



The bones of the top of the skull a:<i pretty well known, and the 

 skull as restored agrees quite closely with the determinations of 

 Case and other authorities. The septo-maxillaries are present, 

 being found attached by matrix to the posterior end of the pre- 

 maxillary. These were displaced in relation to one another, and I 

 have been unable to articulate them with any degree of confidence 

 of their being correctly placed. 



In figure 3, I present a view of the palate of No. 8635, U.S.N.M., 

 which in the main agrees closely with Broom's restoration of this 



» Bull. Amer. Mus. Nat. History, vol. 28, 1910, p. 193, fig. 4. 



