DIVISIONS OF ItEPTILIA. 275 



were gigantic marine Reptiles, cliiefly characteristic of the formations known 

 as the Lias and Oolites. As regards the habits of the Plesiosaurus, Dr Cony- 

 beare concludes : " That it was aquatic is evideut from the form of its paddles ; 

 tliat it was marine is almost equally so from the remains with which it is uni- 

 versally associated ; that it may have occasionally visited the shore, the resem- 

 blance of its extremities to those of the Turtle may lead us to conjecture ; its 

 movements, however, must have been very awkward on land ; and its long neck 

 must have impeded its progress through the water, presenting a striking con- 

 trast to tlie organisation which so admirably fits the Ichthyosaurus' to cut 



Fig. IQ^.—Plnsiosaurusdolichodeirus. Lias. 



through the waves. " As its breathing-organs are such that it must of neces- 

 sity have required to obtain air frequently, it may be inferred " that it swam 

 upon or near the surface, arching back its long neck like a swan, and occasion- 

 ally darting it down at the fish which happened to float within its reach. It 

 may perhaps have lurked in shoal-water along the coast, concealed amongst 

 the sea-weed, and, raising its nostrils to a level with the surface from a con- 

 siderable depth, may have found a secure retreat from the a.ssaults of powerful 

 enemies ; whilst the length and flexibility of its neck may have compensated 

 for the want of strength in its jaws and its incap.acity for swift motion through 

 the water." 



Order VII. Pterosauria. 



The Eeptiles of this order are all extinct, and, like those of the preceding 

 orders, are exclusively confined to the Secondary period of geology. The most 

 familiar examples are the so-called Pterrodactyles, and the distinguishing char- 

 acters of the order have reference to the fact that they were all adapted for an 

 aerial life. They present, in fact, an extraordinary combination of the charac- 

 ters of Birds and Reptiles, and they make also some approach to the Mammalian 

 order of the Bats. In the presence of teeth in distinct sockets, and, as we shall 

 see hereafter, in the structure of the fore-limbs, the Pterodactyles differ alto- 

 gether from all living birds ; and there can be little doubt as to their being 



