THE GREAT FISH-LIZARDS. 



43 



and the hinder or pelvic pair no doubt were of great service 

 in helping the creatures to come up to the surface when 

 necessary. 



Thus we see that the whale, with its one pair of paddles, has a tail 

 specially planned with a view to rapid vertical movement through 

 the water ; while in the fish-lizards, who did not require to breathe 

 so frequently, the tail-fin was planned with a view to swift and 

 straight movement forward as they pursued their prey, and they 

 were compensated by having bestowed upon them an extra pair 



Fig. 4. — (a) Lateral and (B) profile views of a tooth of Ichthyosaurus 

 platyodon (Conybeare), Lower Lias, Lyme Regis, Dorsetshire, (c) Tooth of 

 Ichthyosatcrtcs coiuj?iuitis {ConyhQax^), Lower Lias, Lyme Regis, Dorset. 



of paddles. Thus we learn how one part of an animal is related 

 to and dependent upon another, and how they all work together 

 with the greatest harmony for certain definite purposes (see 

 p. 6). 



These great marine predaceous reptiles literally swarmed in 

 the seas of the Lias period, and no doubt devoured immense 



