1904.] TRIASSIC REPTILE TELERPETON ELGINENSE. 479 



It is extremely regrettable that our knowledge of the American. 

 Ootylosauria should still be so meagre, but what we know shows 

 them to be a type closely related to the Pariosavirians, though 

 differing from them in at least one important character, the 

 absence of the cleithrum. The same may be said of the Proco- 

 lophonia {Procoloplion and Telerpeton\ and therefore these must 

 be regarded, in the light of our present knowledge, as pertaining 

 to the same group, for which the eai'lier name Cotylosaui-ia should 

 be used. 



The order Ootylosauria may be defined as thecodont Reptiles 

 with the temporal region roofed over (without or with a single 

 temporal foramen), with clavicles and interclavicle, with coracoids 

 and prsecoracoids (epicoracoids), without or with a very vestigial 

 plastron, and with the number of phalanges as in typical Reptiles. 

 The absence of cleithi'a and the presence of moi-e than 2.3.3.4.3 

 phalanges * distinguishes them from the Pariosauria ; the second 

 charactei' and the roofing ovei- of the postorbital part of the 

 skull distingviish them from the Anomodontia ; whilst the 

 presence of ossified prajcpracoids and the absence or extreme 

 reduction of the plastron separate them from all the other 

 primitive orders, such as Rhynchocephaha, Plesiosauria, Theco- 

 dontia, &c.,with the possible exception of the Pelycosauria, which 

 likewise flourished in Permo-Triassic times. 



The order Ootylosauria woiild comprise four families, the 

 definition of the American types being derived from the contribu- 

 tions of Cope t and of Oase +. 



A. Supratemporal roof broad, orbit small, nearlj' in the middle of the length of 



the head ; no latero-temporal vacuities ; upper surface of skull more or less 

 sculptured. 

 Teeth small, not transversely expanded, in two rows in the 



posterior part of the javi's 1. Fariotichidce. 



Lateral teeth large, with the crowns expanded transversely to 



the axis of the jaw, ju a single series 2. Diadeciidee. 



B. Supratemporal roof narrow, orbit very large ; skull smooth ; lateral teeth 



expanded transverselj' to the axis of the jaws. 



No latero-temporal vacuity 3. Telerpetidce. 



A small latero-temporal vacuity 4. Frocolaphonidte. 



In his important memoir quoted above, Prof. Osborn has 

 proposed a diphyletic arrangement of the Reptilia with which I 

 would be disposed to agree but for the inclusion of the Ohelonia 

 and Plesiosaui-ia in the iSynapsida, which comprise the Pariosauria, 

 Ootylosauria (exclusive of the Procolophonia), and Anomodontia, 

 and of the Procolophonia in the other subclass, named Diapsida. 

 Both subclasses were evidently derived fi-om Stegocephala with 

 the temporal region completely roofed over. The Pariosauria 

 were probably connected with the Labyrinthodontia and led to 



* I cannot understand what can have induced Dr. Broom to restore Pariosaiiriis 

 with 3.3.4.5.4 phalanges in the manus and in the pes. The formula is 2.3.3.4.3 in 

 the specimen in the British Museum. 



t Proc. Amer. Philos. Soc. xxxiv. 1895, p. 436. 



I Zool. Bull.iii. 1899, p. 231. 



