400 



REPTILES 



xv. 4- 



dorsal portion of the girdles, so well developed in terrestrial reptiles, 

 was here small: the ilium hardly articulates with the sacral verte- 

 brae. The hands and feet were enlarged by increase in number of 

 joints (hyperphalangy), but there was no increase of digits (hyper- 



^^ammssk 



-.-E» 



Lariosaurus 





^^^Mmmrn^ ^ 



Muraenosaurus 



y 



Ichthyosaurus \ Jf 



Fig. 228. Icthyosaurs, plesiosaurs, and their allies. (Partly after Romer.) 



dactyly) such as is seen in ichthyosaurs. The skull was as in notho- 

 saurs, but with the nostril still further displaced on to the upper 

 surface. 



These animals were numerous in Jurassic and Cretaceous seas and 

 some of them reached 50 ft in length. They were obviously fish- 

 eaters, but little is known of their habits. It is not known whether they 

 were viviparous or came ashore to lay eggs. *Placodus and related 



