PRE-JURASSic TETRAPODS. 179 



Epipodials long and separated. Caudal region not much 

 deflected. 



Fam. MixosAURiN^. With five digits. 



Mixosaurus. M. Trias, Italy, Germany, Spitzbergen, 



W. N. America. 



Fam. BhastasaurinjE. Narrow paddles with three or four digits. 

 Cymhospondylus. 



Toretocnemus. 

 Merriamia. 

 Shastasaurus. 

 Deljjhinosaurus. 



M. Trias, Nevada. 



Super-Order AROHOSAURIA. 



Reptiles with a skull with two temporal openings. Brain-case 

 much narrowed between the ears, usually surrounded by bone in 

 advance of the prootic. Paroccipital process antero-posteriorly 

 compressed and long, with the fenestra ovale opening on its 

 lower edge. 



A single coracoidal element. 



Order Thecodontia. 



Primitive Archosaurians with clavicles and an interclavicle. 

 Pelvis " plate-like." 



Family "Eosuchid^." 

 Thecodonts with intercentr-a throughout the column. 

 ^^ Eosicchus" Watson. U. Permian, S. Africa. 

 Youngina Broom. ,, ,, 



Family Erythrosuchid^, nov. 



Very large semiaquatic Thecodonts with a twisted humerus 

 with much expanded ends. Anterior mai-gin of pubis suddenly 

 deflected. Feeble dorsal armour. 



Erythrosuckus Broom. M. Trias, S. Africa. 



Family PHYTOSAURiDJi; McGregor. 



Large Thecodonts, with an elongated rostrum formed mainly 

 by the premaxilla. Dorsal and ventral scutes. 

 Mesorhinus Jaekel. L. Trias, Germany. 



Palceorhinus Williston. M. ? Trias, Wyoming. 

 Phytosau7'us Jaeger. U. Trias, Wurttemberg and U.S.A. 



Mystriosicchics Fraas. ,, ,, 



Rhytidodon Emmons. ,, U.S.A. 



'iStagonolejns Agassiz. M. Trias, Scotland. 



