CHAPTER III 



HAL" NTS AND HABITATS 



The haunts of reptiles in past times, and at the present day. The sea- 

 iguana. Dearth of reptiles in polar and sub-polar regions. Haunts of tort* 

 and snakes. Tree-dwellers. Burrowers. Island forms. Geographical distribu- 

 tion, difficulties of interpretation. Relation to temperature, moisture, etc. Hiber- 

 nation and aestivation. 



DURING the earlier and middle stages of their long and 

 eventful history, when they were the dominant verte- 

 brates other than fishes, reptiles, as will be more fully 

 shown in the sequel, were adapted to occupy every station on 

 the earth, and to fill every rfile in life. The ichthyosaurs and 

 plesiosaurs, and later on the extinct sea-serpents ( Pythono- 

 morpha), together with numerous turtles and a peculiar group 

 of crocodiles, were denizens of the ocean, in which the three 

 first-named groups played the part now taken by whales in the 

 scheme of creation. 1 The pterodactyles, or flying saurians, were, 

 on the other hand, inhabitants of the air, where, so far as their 

 power o( flight permitted, they took the place now occupied by 

 birds. It is, however, improbable that any of these creatures 

 were adapted to a purely pelagic existence comparable to that 

 of the albatross and the tropic-bird at the present ; and, indeed, 

 we do not even know whether they were capable of swimming 

 on the surface of the sea after the fashion of modern sea-birds. 

 Again, to what extent the}' were adapted to an inland life is 

 likewise uncertain, the great majority of their remains having 

 been obtained from shore-deposits, such as the Lias, although 

 some have been found in the Chalk which was probably de- 

 posited in deeper water. It is true indeed that in the Stones- 

 field Slate of Oxfordshire remains of pterodactyles are found in 

 association with those of mammals and other land animals, but 



1 The Middle Jurassic OfhthaJmosaurus appears to have been more com- 

 pletely pelagic than any of the other ichthyosaurs. 



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