Revietcs — Per^nian Reptiles, North America. 519 



margin of the quartzite, and containing the bounder bed and the limestone 

 close by ; further north we have the same group again. In the first- 

 case we have isoclinal folding ; in the second, buckled folding, or 

 Moine gneiss. 



I. — The Permian Amphibia and Eeptilia of North America. 



^^HE recent appearance of three' very important works dealing- 

 with the fauna of the 'Permian' of Texas and the traces of 

 that fauna which have been found in New Mexico, Pennsylvania, 

 etc., enables us for the first time fully to appreciate its importance 

 and its many remarkable features. Evidence has been recently 

 accumulating to show that this fauna is really largely of Upper 

 Carboniferous age. Williston has pointed out that the fauna is an 

 isolated one, apparently developed quite out of touch with the rest 

 of the world; and although Broom has shown that it is composed of 

 fundamentally the same stocks as the Permian fauna of South Africa, 

 there is no doubt that his general argument is correct. 



It is a ver}' remarkable group of animals which on a ground plan 

 of very primitive structure have built up astonishing specializations, 

 so much so that types like Cacops, Dimetrodon, and Edapliomurus 

 are amongst the most bizarre animals known. These animals, and 

 many others, seem to exhibit all the features which usually occur in 

 the last individuals of a race : they are phylogerontic, and it is 

 improbable that they left any descendants. 



The ' Texas ' amphibia and reptiles are then in general precociously 

 specialized examples of the early stocks which in South Africa slowly 

 developed along many lines and gave rise to the mammalia amongst 

 other groups. In the light of these ideas it is of interest to examine 

 some of them in more detail. Diplocaul%(,s, now nearly completely 

 known, is an extraordinarily specialized type with an enormous flat 

 head, much produced over the ears, with a slender body and very 

 reduced pectoral limbs. Nothing like it is known elsewhere, but it 

 seems to be a terminal member of the line of Microsauria represented 

 by Ceraterpeton and Biceratosaurus, which occurs in Europe and 

 North America. 



The imperfectly known TrimeroracMs is a rather unspecialized 

 type, interesting because of its close similarity with the South African 

 IJpper Permian Bothriceps Huxlexji, now more completely known. 

 The large and very well-known Eryops is a specialized representative 

 of a type represented in Europe by Actinodon, and in South Africa 

 by Rhinesuchus or Ih/riodon, a type Avhose structure as completely 

 shown by specimens in the Pretoria Museum is thoroughly Eryopid, 

 although much more generalized. 



The extraordinary type Trematops, yqvj reptilian in appearance, 

 has no recognizable allies elsewhere, and the still more remarkable 



■^ E. C. Case, A Bevision of the Ampliibia and Pisces of the Permian of 

 North America, Carnegie Institution, Pub. 146, Washington, 1911 ; A Revision 

 of the Cotylosauria of North America, Carnegie Institution, Pub. 14.5, 1911. 

 S. W. Williston, American Permian Vertebrates, University of Chicago 

 Press, 1911. 



