50 



VERTEBRATA. 



ORDER SAUROPTERYGIA. 



The type of this order is the genus Plesiosaurus, which is 

 sufficiently described below. 



The group ranges through the Jui-assic and Cretaceous of 

 Europe, where the greater number of species are found, sixteen 

 species occurring in Great Britain alone. Thirteen species have 

 been named from the American Cretaceous, but they are more 

 related to the European Pliosaurus than to the type genus. 

 They are all marine, and some of vast dimensions; the Elasmo- 

 saurus of America was forty -five feet long. 



It is supposed that the members of this order could inhale a 

 large quantity of air so as to bear submergence for some time ; 

 although they kept to shallower waters, unlike in the latter respect 

 to the IcJitliyosaur'US. No trace of any derma-skeleton has been 

 found. 



No. 74. [225] Plesiosaurus dolichodeiniS, Conybeare. 



Skeleton, on slab (cast). The Plesiosaurus was first discovered in 1823, by 

 Conybeare and De la Beche. Ciivier thought "its structure the most singular, 

 and its characters the most anamolous that had been found amid the ruins of 

 a former world." "To the head of a Lizard (wrote Buckland) it united the 

 teeth of a Crocodile, a neck of enormous length, resembling the body of a 

 Serpent, a trunk and tail having the proportions of an ordinary quadruped, 



the ribs of Chameleon, and the paddles of a Whale." The skull is three times 

 longer than its breadth, and subcompressed. The cranium is quadrate; nostrils 

 small and situated near the ej^e; teeth slightly recurved, striated, sharp, long, 

 and slender, lodged in distinct alveoli, — the anterior being the longest. The 

 swan-like neck consists of from twenty to forty vertebrte, while living reptiles 

 have not over nine cervicals. The pectoral arch is remarkable for the greatly 



