THE GREAT SEA-LIZARDS 83 



more " tugging and riving." So with regard to its body, pro- 

 bably some hungry creature had a grip of the spine near the 

 middle of the back, and pulled all the succeeding vertebrae in the 

 region of the hind limbs. Thus we get a little glimpse of scenes 

 of violence that took place at the bottom of the bright sunny seas 

 of the period when the clays and limestones of the Lias rocks 

 were being deposited in the region of Lyme Eegis. 



As time went on, these curious reptiles increased in size, until, 

 in the period when our English chalk was being formed (Creta- 

 ceous period), they reached their highest point (see p. 197). After 

 that they became extinct whether slowly or somewhat suddenly 

 we cannot tell. 



Until more is known of the ancient life of the earth, it will not 

 be possible to say with certainty what were the nearest relations 

 of the long-necked sea-lizards. They first appear in the strata 

 of the New Eed Sandstone, which is below the Lias. Certain 

 little reptiles, about three feet long, from the former rocks, known 

 as Neusticosaurus and Lariosaurus, seem to be rather closely 

 related to the creatures we are now considering, and to connect 

 them with a group of land reptiles. They were partly terrestrial 

 and partly aquatic; but it is not easy to say whether their 

 limbs had been converted into true paddles or not. At any 

 rate, there is every reason to believe that the long-necked sea- 

 lizards were descended from an earlier form of land reptile. 

 They gradually underwent considerable modifications, in order to 

 adapt themselves to an aquatic life. We noticed that the same 

 conclusion had been arrived at with regard to the fish-lizards. 

 Both these extinct groups, therefore, present an interesting 

 analogy to whales, which are now considered to have been 

 derived, by a like series of changes, from mammals that once 

 walked the earth. 



