180 



MR. D. M. S. WATSON ON 



Family Ornithosuchid^: v. Huene. 



Small, slightly built Thecodonts. Pointed skull without pro- 

 duced rostrum. Pubis and ischium much produced. 

 Hinder limbs longer than the fore. 

 ? Directly ancestral to Theropodous Deinosaurs. 

 Orniihosuchus E. T. Newton. M. Trias, Scotland. 

 Euparkeria Broom. ,, S. Africa. 



Scleromochlus A. S. Woodward. ,, Scotland. 

 Sphenosuchus Haughton. U. Trias, S. Africa. 



Family Aetosaurid^e Baur. 



Small Thecodonts with a pointed skull without rostrum, pubis 

 and ischium short. Hind limbs not greatly larger than the fore. 

 A very heavy dorsal and ventral armour. 



Aetosaurus Fraas. IT. Trias, Wiirttemberg. 



IDyoplax „ „ „ 



? Stegomus Marsh. ,, U.S.A. 



? Notochampsa Broom. ,, S. Africa. 



Family Howesiice, nov. 



? Thecodonts with several rows of teeth in the maxilla. 



Howesia Broom. M. Trias, S. Africa. 

 IMesosuchus Watson. „ ,, 

 ViProterosuchus Broom. ,, 



Family Erpetosuchice, nov. 



Small Thecodonts with a pear-shaped skull, not very elongated 

 rostrum. Palate incipiently secondary, with the posterior nares 

 in a deep groove. 



? Ancestral to the Orocodilia. 



Erpetosuchus E. T. Newton. M. Trias, Scotland. 



Order Saurischia Seeley. 



Archosauria with the astragalus very closely and immovably 

 articulated with the tibia. Pelvis with the pubis and ischia long 

 and projecting downward, usually with an ischio-pubic vacuity. 



Thecodontosaurus Riley & Stutchbury. IT. Trias, Somerset- 

 shire, Swabia, S. Africa, Queensland ; 

 and very many forms representing numerous families, defined 

 especially by v. Huene. 



Order Rhynchocephalia Giinth, 



Reptiles with a two-arched skull, a short, high brain-case not 

 ossified in advance of the prootic, and large fenestra ovale. Teeth 

 on the dentary biting into a groove between the maxillary and 

 palatine teeth. 



