6 THE MORPHOLOGY OF THE SKULL 



clay by simple washing with a soft sponge, so that all the most minute details of 

 structure and sculpture are clearly made out. 



Specimen No. 1002 was preserved in a compact red clay, and the bones were 

 covered with a hard scale of calcareous material, which was removed with comparative 

 ease, leaving the bones hard and perfect. This skull is unique in the perfection of its 

 preservation, the only portions missing being the temporal arches, in part, of the left 

 side and the median portion of the epipterygoids. The skull lay on its side, and all 

 the bones are joined in their natural relations. The whole skull has been crushed 

 slightly from the sides, so that it is seemingly more narrow than it really is. The 

 bones of the top of the skull have been slightly broken and the palate has been pushed 

 slightly downward, but on the whole the skull has been so little changed from its 

 natural condition in life that it is easily restored. 



The four specimens are evidently of the same genus, Dimetrodon, of the Pelyco- 

 sauria but do not belong to the same species ; it is impossible to state their specific 

 position exactly in the present state of our knowledge, but the specimen numbered 1 

 has been described (Baur and Case, '99) as Dimetrodon indsivus ; number 114 as 

 Dimetrodon {Embolophorous) dollovianus (Case, '03) ; number 1001 is undetermined 

 but stands very close to number 1 ; number 1002 is almost certainly Dimetrodon gigas. 

 No attempt will be made in this paper to point out specific distinctions, the object 

 being solely to give an accurate account of the skull of the genus Dimetrodon as an 

 example of the skull of the Pelycosmiria in general. The restored skull is made up 

 almost entirely from the skull of D. gigas (No. 1002) and may be accepted as a very ac- 

 curate account of the skull of that species, as so little has been used from other sources. 



In the original descriptions of specimens 1 and 114 (Baur and Case, '99 ; Case,'03) 

 an error was made in considering the articular region of the lower jaw as the articular 

 region of the skull proper ; this led to an unfortunate series of comparisons and specu- 

 lations which must be in large part abandoned as based on false assumptions. Notable 

 among these was direct comparison of the Pelycoscmria Avith the Theriodonts of South 

 Africa {Cynognathus and Gomphognathus) ; this error was due to the supposed depres- 

 sion of the quadrate bone and its almost complete disappearance under the suspensorial 

 bones, a condition very close to that of the African forms ; the demonstration that 

 this condition is not found in the Pelycosaurs removes them from any possible connec- 

 tion with the Theriodonts though newly discovered structures place them, probably, 

 rather nearer to the TJierocephalia of Broom ('03). The error here cited has- already 

 been corrected in two papers (Case, '04, '04'). 



The discovery of the elevated condition of the quadrate region shows that the 

 restoration of the skull previously published (Baur and Case, '99) was too short in the 



