472 Lull — Functions of the '"'Sacral Brain^^ in Dinosaurs. 



saurus, they are sharp-pointed and compressed, with 

 finely serrated cutting edges. In Tyrannosaurus they 

 become so thick that the knife-like edge is gone, so that 

 these hnge beasts must have dismembered their prey by 

 tearing rather than by cutting it. These latter thero- 

 pods are analogous to the crocodiles in dental equipment ; 

 Allosaurus, on the other hand, possessed a more efficient 

 dentition. 



The digestive system of the crocodiles shows the high- 

 est degree of specialization of any living reptiles, as the 

 stomach is very muscular, with lateral tendinous discs 

 forming an organ very suggestive of the gizzard of the 

 graminivorous birds. In front of this gizzard-like stom- 

 ach is a capacious portion of the oesophagus, within which 

 is held the excess of food over the rather small capacity 

 of the stomach. The stomach digestion is highly effici- 

 ent, due not alone to its muscular power, but to the 

 strength of the gastric juice, so that even the bones of 

 the prey, are dissolved and not passed through the intes- 

 tine, as with certain carnivorous birds like the owls. 

 Crocodiles occasionally swallow stones to aid in the tri- 

 turation of their food, just as do the graminivorous birds. 



To what extent the gizzard was developed in the 

 Theropoda is conjectural, but it would seem as though 

 its need were nearly as great with them as with the 

 crocodiles. One aberrant type of theropod, Struthiomi- 

 mus, from the Belly River formation of Canada, has just 

 been the subject of an authoritative paper by Professor 

 Osborn.^ This form is now knoA\ni to have been abso- 

 lutely toothless, and several theories have been advanced 

 as to its feeding habits — that it was insectivorous, espe- 

 cially ant-eating, or that it fed on small crustaceans or 

 molluscs of the seashore, or that it was ostrich-like in 

 habits, browsing upon leaves and buds which its prehen- 

 sile limbs drew within the reach of the horn-sheathed 

 mouth. Such an assumption as the last, which bears the 

 weight of Osborn's own opinion, would seem to imply the 

 presence of a more or less efficient gizzard-like stomach 

 functionally comparable to that of the struthious birds. 



Sauropoda. — The sauropods are clearly of theropod 

 derivation, but it has been pretty generally assumed that 

 they had forsaken the carnivorous habits of their for- 



^ H. F. Osborn, Skeletal adaptations of Ornitliolestes, Struthiomimus, 

 Tyrannosaurus, Bull. Amer. Mus. Nat. Hist., vol. xliii, 1917, pp. 733-771. 



