GEOLOGY. 555 



belemnites, plagiostomata, and encrinites, which are pecul- 

 iar to it. But what impresses a special stamp upon it is 

 the presence of strange marine reptiles, the remains of 

 which are found in it remarkably well preserved. 



At this time lived the Ichthyosauri, veritable fish-lizards, 

 as is indicated by their name. These reptiles, which must 

 have spread terror through the ancient seas, attained a 

 length of about thirty-three feet. Their whole organization 

 is a series of paradoxes. With the vertebrae of the fish they 

 have the fins of a dolphin ; and while armed with the teeth 

 of a crocodile they display an optic globe which is without 

 any parallel. This eye, the bulk of which was sometimes as 

 large as a man's head, was protected in front by a frame- 



220. Head of Ichthyosaurus: Ichthyosaurus communis. 



work of bony plates, and was beyond all doubt the most 

 powerful and perfect visual apparatus ever seen in creation. 

 Hence Buckland maintains that the Ichthyosauri could dis- 

 cover their prey at the greatest as well as the shortest dis- 

 tances ; in the profound darkness of night, and in the depths 

 of the ocean, the delicate structure of the organ of vision 

 being protected from the pressure of the water and the 

 shock of the waves by the osseous buckler which surrounds 

 the transparent cornea. 



Naturalists have investigated the remains of these ani- 



