4 E. C. CASE 



left side with part of the fore limb of the right side, the pelvis 

 nearly perfect on both sides, and parts of the bones of the posterior 

 limb are all preserved. Thirty-five vertebrae, beginning with the 

 atlas and terminating with several caudals, represent the verte- 

 bral column; it is possible that the column is not complete, but, 

 considering the series and comparing it with Cope's published 

 figure of the vertebral column of the Dimetrodon^ it seems that 

 only the end of the tail and possibly a few anterior dorsals are 

 missing. The figure given by Cope shows the column complete 

 to the second sacral. The dependent portion figured as a part 

 of the attached pelvis on one of the vertebrae is the rib of the first 

 sacral, such as is shown in Figs. 20 and 21, but covered by a 

 portion of the matrix. The peculiar shortening of the lumbar 

 vertebrae is evidently just beginning. There are twenty-five 

 presacrals figured by Cope, but there is a break between the 

 twentieth and twenty- first; there are twenty-seven in the present 

 specimen. From the seeming necessity of proportions and 

 because of the uncertainty as to the correct number, I have added 

 four vertebrae in the anterior dorsal region, making the total 

 thirty-two. This may be too many. The numbers given to the 

 vertebrae in the following descriptions are such as indicate their 

 position in the accompanying restoration, and are arbitrary in 

 that the vertebrae were not all discovered in series, but have been 

 located by their anatomical peculiarities. Beginning with the 

 seventh presacral, the series is complete and was found in posi- 

 tion to the second caudal. 



The skull. — The individual bones of the skull show such 

 slight differences from the bones of the skull of Dimetrodoii inci- 

 sivus already described by the author (i) that it is unnecessary 

 to repeat the descriptions. In Fig. i is given a side view of the 

 skull, showing the bones in their natural positions ; the bones 

 are so slender and the matrix so hard that it has been impossi- 

 ble to remove it all from the bones ; in consequence the drawings 

 have been made somewhat diagrammatic, but this has been done 

 only so far as necessary to eliminate the matrix; the relative 

 positions of the bones, and even their distortion, has been pre- 



'^ Proc. Aj?i. Phil. Soc, August, 1880, Figs. 3 and 3a, PI. VI. 



