THE EVOLUTION THEOKY 109 



Its entire body was adapted to a life in the water ; its extremi- 

 ties, consisting of an enormous number of single bones, were 

 transformed into an ideal rowing-apparatus. The long tail ended 

 in a large perpendicular fin, whilst the back carried another 

 powerful fin. Like the Plesiosaurus, the Ichthyosaurus was a 

 voracious animal of prey whose food consisted chiefly of fishes 

 and molluscs. As was proved by some interesting discoveries of 

 female individuals, the Ichthyosauri were viviparous. The 

 Plesiosauridse are remarkable for their long swanlike neck which 

 carries a relatively small head. 



When we leave the sea and. turn to the coast and the river 

 courses we meet large crocodile-like reptiles of which the 

 Teliosaurus and Belodon may be mentioned. On the land lived 

 the members of the giant Atlantosaurus family, of which the 

 enormous Brontosaurus is the best-known representative. 



If previous exaggerated statements which gave the length 

 of these animals as about 36 metres and their height as 8 to 

 10 metres have been reduced by modern researches to 22 and 

 5 metres, these giants must, nevertheless, have created the 

 impression of walking houses, and even our largest elephants 

 would have been completely dwarfed by them (see coloured 

 plate). Nevertheless^ there is no ground for believing that pre- 

 historic animals were much larger than living forms. The 

 Greenland whale (Balcena mysticetus) equals in size the largest 

 Brontosaurus ; our modern land mammals, the elephant, giraffe, 

 rhinoceros and hippopotamus are as large as any Saurian, and 

 there are few animals in prehistoric time which equalled, let 

 alone exceeded, our Cachalot (Physeter macrocephalus) , with its 

 length of 18 to 20 metres. That fossil reptiles, nevertheless, 

 appear to have been possessed of enormous dimensions is due to 

 a subjective reason. 



A horse 3 ft. high looks small, and a dog of the same 

 height would look gigantic, because we are accustomed to seeing 

 larger horses and smaller dogs. Prehistoric animals do not in 

 fact exceed the present forms in size, but we find that individuals 

 of certain fossil classes possess far larger dimensions than their 

 modern congeners. This is especially true as regards reptiles. 

 Because to-day lizards about a foot in length, and snakes 10 ft. 

 long seem large to us, it is not surprising that the relatively 



