E. C. Case — Dimetrodon inclsivus. 



475 



From the very abundant material sufficient bones of the right 

 size have been selected to mount a nearly complete skeleton of 

 Dimetrodon incisivus Cope. The work of mounting this speci- 

 men necessitated a careful study of the possible attitudes and 

 movements of the animal which is reflected in the completed 

 work. The skull in the mount is restored in plaster, except 

 the anterior portion of the lower jaws, from fragments in the 

 collection and from careful studies upon the perfect specimen 

 of a skull of this species in the American Museum of Natural 

 History in New York and upon a very perfect specimen of 



Fig. 2. 



Fig. 2. Photograph of the restored skull, all plaster except the anterior 

 portion of the lower jaw, with the teeth. x - 13. 



the skull of Dimetrodon gigas in the possession of the author. 

 The notably large size of the skull led to a very critical study 

 of the proportions to check the apparent incongruity and the 

 author feels sure that the proportions shown in the skeleton 

 are correct. As mounted, the skull is raised slightly from the 

 ground but is still inclined somewhat downward in an attitude 

 of partial repose. From the position and character of the cer- 

 vical vertebras it is apparent that the head could not have been 

 raised very much higher, except as it was violently forced 

 upward in a moment of anger or attack. 



The body is placed in an attitude of repose ; the posterior 

 end of the interclavicle rests upon the ground and the symphy- 

 sis of the pubes is raised only sufficiently to allow for the car- 

 tilages which were present during life. In this attitude the 



