648 GEOLOGY. 



morphs or anomodonts) whose relationships and significances yet 

 await resolution, for the greater part. Under the theromorph lineage 

 are perhaps to be placed the turtles and plesiosaurs that appeared 

 later. The more generalized or stegocephalian-like forms of the latter 

 group have been given an ordinal rank as the Pareiasauria or Cotylo- 

 sauria by some authors, who regard them as ancestral not only to 

 the Theromorpha, but to the rhynchocephalian type of reptiles as 

 well, thus giving expression to the view that the differentiation had 



Fig. 300. — -A fin-back lizard of the Permian of Texas (Dimetrodori) . The skeletons 

 found vary from three to ten feet in length. (Restored by Case.) 



occurred after the attainment of the reptilian form. Other group- 

 ings are made by other authors, implying that a final opinion is not 

 yet universally reached. 



The more distinctively reptilian group (Diapsida). — The Palceohatteria 

 of the Lower Permian of Saxony, a small, long-tailed, lizard-like reptile, 

 is recognized at present as the pioneer of this branch (Fig. 299). It 



