474 



MANUAL OF ZOOLOGY. 



have occasionally visited the shore, the resemblance of its ex- 

 tremities to those of the Turtles 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 contrast to the organisation which 

 so admirably fits the Ichthyosaurus to cut through the waves." 

 As its respiratory organs were such that it must of necessity 

 have required to obtain air frequently, we may conclude " that 

 it swam upon or near the surface, arching back its long neck 

 like a swan, and occasionally darting it down at the fish which 

 happened to float within its reach. It may, perhaps, have 



Fig. 207. A, Skull of Dicynodon lacerticeps, showing the maxillary tusk. B, Skull of 

 Oudenodon Bainii. From the Trias of South Africa. (After Owen.) 



lurked in shoal water along the coast, concealed amongst the 

 sea-weed ; and raising its nostrils to a level with the surface 

 from a considerable depth, may have found a secure retreat 

 from the assaults of powerful enemies ; while the length and 

 flexibility of its neck may have compensated for the want of 

 strength in its jaws, and its incapacity for swift motion through 

 the water." 



The geological range of the Plesiosaurus is from the Lias to 

 the Chalk inclusive, and specimens have been found indicating 

 a length of from eighteen to twenty feet. 



Of the other genera of the Sauropterygia, Simosaurus and 



