Dinosauria — Theropoda, 



13 



gascariensis from the Jurassic rocks of Madagascar. From S, 

 America a few vertebrae of Tltanosaurus australis, from, the 

 Cretaceous rocks of Patagonia, are exhibited. 



Sub-order 2. — Theropoda (Beast-footed). 



The Theropoda hokl an intermediate position between the Wall-case, 

 Sauropoda and the Ornithopoda, although more nearly allied ^°- '^• 

 to the former. In the structure of the teeth, the form of the 

 femnr, the occasional presence of only two sacral vertebra?, 

 and in the form of the quadrate bone, certain genera approach 

 moi'e nearly to the Crocodilia than even do the Sauropoda ; 

 although in their hollow limb-bones they agree Avith the 



Fig. 15.— Left side of pelvis of AUosaurus fmriilis (Marsh), from the Upper Jurassic 

 of North America (Jj nat. size), n, acetabulum ; (7, ilium; j), pubis; is, ischium 

 (after Marsh). 



Ornithopoda. All the forms were carnivorous. The premax- 

 illary was furnished throughout with teeth, which are laterally 

 compressed and backwardly curved, the cutting edges of one or 

 both of which are frequently serrated. The teeth are planted 

 in distinct sockets, and the skull has a large aperture in front of 

 the eye, known as the preorbital vacuity. The centra of all the 

 vertebra? are hollowed internally, and much compressed laterally. 



