90 THE EXTINCT BATRACHIA, REPTILIA 



Length ft. 

 Polyacanthus, Owen, 9 



Scelidosaurus harrisonii, Owen, 12 



Iguanodon anglicus, Meyer, 28 



Hylaeosaurus armatus, Mant, 21 



Hadrosaurus fonlkei, Leidy, 28 



Poecilopleurum bucklandii, Deslong, 25* 



Megalosaurus bucklandii, Mant, 1 30* 



Laelaps aquilunguis, Cope, 24 



Teratosaurus suevicus, Meyer, 1 30 



Ornithotarsus immanis, Cope, % 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. It 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 further resembled Crocodilia in having the lateral lobes of the 

 cerebellum developed, and the vermis plicate. 



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

 is very slight ; the Crocodilia, though somewhat removed, are the nearest Jiving 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 have 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 Triassic 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. 



ORTHOPODA. 



Cope Prcc. Acad. Pliila., 1S66, 317. Therosauria Haeckel, 1861 



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

 tibia and with a terminal face 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. 



