THE PERMIAN PERIOD. 



649 



was typically rhynchocephalian, and is notable in that its line of descent 

 is perpetuated to this day in the 

 Sphenodon or Hatter ia of New Zea- 

 land. With kindred genera it con- 

 stitutes the suborder Proterosauria. 

 Representatives have been found in 

 England, Scotland, France, and Bo- 

 hemia. They are not known in North 

 America. An allied suborder {Pely- 

 cosauria) is predominantly American, 

 and was represented by several genera 

 (Clepsydrops, Embolophorus, Di metro- 

 don, Naosaurus, etc.) in Texas, Il- 

 linois, 1 and Kansas. There were 

 also representatives in Europe. The 

 skeletal features of one of the more 

 typical genera, as worked out by 

 Case, are shown in Fig. 300. A 

 third suborder (Proganosauria) which 

 some paleontologists believe, to be 

 rhyncocephalian in character, though 

 by others referred to the Saurop- 

 terygia, had two genera (Stereoster- 

 num and Mesosaurus) of small, 

 elongate, subaquatic reptiles (Fig. 

 301), from Brazil and South Africa. 



The mammalian strain of the rep- 

 tilian group (Synapsida). — At pres- 

 ent the Pareiasaurus (Fig. 302) stands as the pioneer of this branch, 

 and presents the nearest approach to the labyrinthodonts. The group 

 seems to have diverged with great rapidity, for it developed markedly 

 varied and strange forms by the close of the period. These diverse forms 

 are grouped under the ordinal term Anomodontia by some authors, 

 and by others under Theromorpha, in which case Anomodontia is restricted 

 to a suborder ( = Dicynodontia) under Theromorpha. The latter term 



Fig. 301. — Stereosternum tumidum, 

 from Brazil, about I natural size, 

 (Restoration by McGregor.) 



1 The locality in Illinois appears to be simply an old river-bed eroded in the sur- 

 face of the Coal Measures, and subsequently filled with alluvium, imbedding the 

 reptilian remains. 



