244 HISTORICAL PALAEONTOLOGY. 



swimming-paddles, whilst the skin seems to have been equally 

 destitute of any scaly or bony investiture. Unlike the Ichthy- 



Fig. 177. Plesiosaurus dolichodeirus, restored. Lias. 



osaur, however, the Plesiosaur had the paddles placed far back, 

 the tail being extremely short, and the neck greatly lengthened 

 out, and composed of from twenty to forty vertebrae. The 

 bodies of the vertebrae, also, are not deeply biconcave, but are 

 flat, or only slightly cupped. The head is of relatively small 

 size, with smaller orbits than those of the Ickthvffsaur, and with 

 a snout less elongated. The jaws, however, were armed with 

 numerous conical teeth, inserted in distinct sockets. As re- 

 gards the habits of the Plesiosaur, Dr Conybeare arrives at the 

 following conclusions : " That it was aquatic is evident from 

 the form of its paddles'; that it was marine is almost equally 

 so from the remains with which it is universally associated ; 

 that it may have occasionally visited the shore, the resem- 

 blance of its extremities 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 strong 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 lurked in shoal water along the coast, con- 

 cealed amongst the sea -weed; and raising its nostrils to a 



