THE GREAT SEA-LIZARDS 83 
more “ tugging and' riving.” So with regard to its body, pro- 
bably sonie 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 Rew Red 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. 
