LIFE IN SECONDARY TIMES 261 



poraneous existence of herbivorous reptiles, or at least 

 reptiles which fed on insects, molluscs, and other small prey. 

 We are thus far from having any knowledge of the food habits of 

 the terrestrial vertebrate fauna of the Trias. 



Perhaps we should see herbivorous vertebrates in Anomo- 

 dontia, represented by several genera distributed from Elgin 

 in Scotland to the Cape. The dentition of these animals is 

 reduced to two tusks in Dicynodon, recalling those of the 

 Walrus ; these canines are short and conical in Gordonia and 

 Geikia of Elgin, and can be present or absent in individual cases 

 in CistecepJialus, suggesting that they are characteristic of the 

 male sex. This would lead us to assume that Oudenodon, which 

 had no tusks at all, was merely the female of Dicynodon. The 

 jaws of this animal, whose skull can attain a length of two 

 decimetres, elongate beyond the tusks and were probably 

 covered by a beak analogous to that of the Chelonians, which, 

 as a matter of fact, were already represented in the Triassic 

 Epoch by several genera. 1 



The Rhynchocephala were represented by Telerpeton. 



Finally, the series of Theromorpha terminates in the Placo- 

 donts, terrestrial animals which had again become marine and 

 lived on molluscs whose shells they crushed with the aid of two 

 or three scissor-like teeth on the intermaxilliary, and three to 

 five rounded upper molars and some flattened teeth borne by 

 the palate and the posterior part of the mandible, arranged 

 like paving-stones. A number of varieties of Crocodiles 

 completed the Triassic reptilian fauna. 



Rhynchocephala, Crocodilians, and Chelonians all became 

 more and more diversified in detail throughout the Jurassic and 

 Cretaceous — two periods most clearly marked with the impress 

 of new ages. The heavy Theromorpha disappeared, but whilst 

 vegetation of marvellous variety flourished, the development of 

 Reptiles positively luxuriated. They had no competitors on 

 land; the earth was theirs, and the constancy of the temperature 

 was particularly favourable to them. No danger menaced 

 the more powerful ; they grew slowly like the Crocodiles of 

 our times, but the length of their peaceful lives was such that 

 some of them were forty metres long. Given that their 

 rate of growth approximated to that of Crocodiles, this would 



1 Chelzytion, Arctosanrus, Psammochelys. 



