90 



THE EXTINCT BATRACHIA, REI'TILIA 



Polyacanthus, Owen, 

 Scelidosaurus harrisonii, Owen, 

 Iguanodon anglicus, Meyer, 

 Hylaeosaurus armatus, Mant, 

 Hadrosaurus foulkei, Leidy, 

 PoecUopleurum bucklandii, Deslong, 

 Megalosaurus bucklandii, Mant, 

 Laelaps aquilunguis, Cope, 

 Teratosaurus suevicus, Meyer, 

 Ornithotarsus immanis, Cope, 



Length, ft. 

 9 



12 



28 



21 



28 



25* 

 VM)* 



24 

 1 30 

 % 35 



Prof. Owen suspects the animals of this order to have had the septum of the ventricles 

 of the heart complete as in the Crocodilia. 1 1 is an interesting inquiry whether there were 

 two aorta-roots or only one, and if one, whether the right or left remained. I have little 

 doubt that the Dinosauria farther resembled Crocodilia in having the lateral lobes of the 

 cerebellum developed, and the vermis plicate. 



The affinity to the modern Sauna, or Lacertilia, which some authors have allowed of, 

 is very slight ; the Crocodilia, though somewhat removed, are the nearest living allies. If 

 we consent to a derivative relation between types, we must consider this order to have given 

 origin by divergence and metamorphosis to both, the Mammalia and Aves. The structure 

 and embryology of the- last two classes forbid the idea that either could lane been derived 

 from the other. 



Besides the differences in the structure of the tarsus and metatarsus observed in this 

 order, there are marked differences in that of the tibia. Thus most of the order present a 

 very prominent spine and crest, of bird-like character; but Plateosaurus Meyer and Tera- 

 tosaurus Meyer both Triassie genera, appear to possess this character in a very slight 

 degree, the former scarcely at all. I have, therefore, not included them in the groups 

 following. 



OETHOPODA. 



Cope Prcc. Acad. Phila., 1866, 817. Tlierotawia Eatektl, 1866. 



Proximal tarsal hones distinct from each other and from the tibia., articulating with a 

 tibia, and with a, terminal fact; of a well developed fibula. The ilium with a massive 

 narrowed anterior prolongation. 



In the few genera of this suborder, of which the teeth have been discovered, a successive 

 divergence from the type of the Goniopoda is visible, in the shortening and increase in 



* These estimates I have reason to think exaggerated. 



