MORPHOLOGICAL REVISION OF THE SUBORDER. 



121 



and some are lost, it is evident that the tail did not exceed one-third of the length of 

 the presacral vertebral column. 



The shoulder girdle of Dimetrodon gigas is unknown. 



The proximal half of the humerus is preserved in the type specimen, No. 4006 

 Am. Mus. It differs from Dimetrodon incisivus in the articular face, which involves 

 the whole of the proximal end, and the radial crest, which, while very strong, is not 

 long, beginning lower down on the head and not continuing so far distally. The 

 edges of the proximal end are quite rugose. 



Th^ pelvis (No. 4006 Am. Mus.) : The crest of the iliiDii is broken away so that 

 its exact form is not certain, but it projected to the rear, as in Dimetrodon incisivus. 

 Cope, in his description of the long axis of the ilium being at right angles to the long 

 axis of the ischium and pubis, did not recognize that the posterior end of the crest was 



Fig. 49. — Anterior view of the same pelvis as shown in fig. 48. Showing the narrow and high pelvic cavity and 



the deep symphysis, s.r, distal end o( sacral rib: pu, pubis; //, ilium. X %. 

 Fig. 50. — Anterior view of the femur of D. gigas, No. 4006 Am. Mus. X ^ ■ 



broken off. The face of the acetabulum is covered with matrix so that it is impossible 

 to locate just the parts taken by the several bones, but it is evident that the ilium 

 descended far down between the ischium and pubis. The edges of the acetabulum 

 are not more raised than in any other species. The anterior euds of the pubis are 

 broken away, so the full length is not known ; so far as preserved the edges of the 

 pubes of the two sides meet in a deep symphysis. The obturator foramen is located 



