122 THE PERMO-CARBONIFEROUS RED BEDS OF 



This goes no further than to state the author's belief that the American 

 and South African forms had developed sufficiently far to indicate their main 

 lines of evolution so clearly that we are able to recognize that they belong to 

 separate phyla. ^ 



As has been repeatedly intimated in this discussion, the group called 



Pelycosauria is now recognized as a composite group, and while I am unable 



to agree with Dr. WilHston that they should be grouped with the South 



African forms as Theromora, I do agree with him in his subdivision of the 



fauna into distinct groups. If I am mistaken in his views, and he is inclined 



to restrict the Theromora to the American forms, as he apparently does in 



his Review of the Primitive Reptiles (p. 649), then I think we are together, 



accepting the Theromora as a provisional order. My arrangements would 



be only slightly different from his: 



Order Theromora. 



Suborder Pelycosauria. 



Family Clepsydropidas (Sphenacodontidas) . 



Family Poliosauridfe. 

 Suborder Edapliosauria. 



Family Edaphosauridae. 

 Suborder Proterosauria. 



Family Paleohatteridse. 

 Suborder Caseasauria. 



Family Caseidae. 

 Suborder Kadaliosauria. 



Family Kadaliosauridac. 



Family Areoscelida;. 



Edaphosaurus can not justly be retained in the Pelycosauria. The genus 

 is as distinct from either Clepsydrops or Dimetrodon as is Casea or Areoscelis. 

 The high spines which gave the original idea of a kinship with Dimetrodon 

 can only be regarded as a parallel character, found also in Platyhistrix. The 

 bones of the skull are uncertain. Case and Broom, not being in accord on all 

 points, and Williston agreeing with neither. But the possible extent of the 

 lachrymal to the nares (Broom and Williston) ; the possible presence of post- 

 parietal bones; the totally different dentitions and diet; the different shape 

 of the axis ; the different proportions of the upper and fore arm and leg ; the 

 presence of an ectepicondylar foramen in the humerus; the different shape 

 of the ilium and femur; the totally different habits of life, are sufficient to 

 place it in a separate suborder. 



The Poliosauridae, generally grouped with the Pelycosauria, are equally 

 close to the Proterosauria, as suggested by Williston. The imperfectly 

 ossified condition of the pectoral and pelvic girdles are explainable upon the 

 hypothesis of an aquatic adaptation, which is borne out by the presence of 

 the sclerotic plates (Williston) , and admitted as possible by Osborn because 

 of the distal expansion of the humerus and the imperfect ossification of the 



" Broom's citation of the similarity of the structure of the jaw in Pelycosauria and Dinocephalia (Bull. 

 Amer. Mus. Nat. Hist., vol. 33, art. 9, 1914, p. 141) is but an instance of a line of a general group which, 

 departing from, or, better, refusing to follow, the manifest destiny of its relatives, suffered the usual fate, 

 extinction. 



