52 



THE STORY OF REPTILE LIFE. 



longer than the fore. Here, however, resem- 

 blance, both to fossil and recent crocodiles ceases, 

 inasmuch as the lizard-like form is completely 

 transformed by adaptation to an exclusively 

 aquatic, and probably marine life. This adapta- 

 tion has produced a remarkable but superficial 

 likeness to its contemporary the Ichthyosaurus. 

 The fore-limbs were paddle-shaped, whilst the 

 hind-limbs were of considerable length, and ter- 

 minated in a broad, webbed foot. They probably 



FIG. 6. Outline Restoration of an extinct Crocodile specially adapted 

 for an exclusively marine life. 



performed the work of locomotion, whilst the 

 tail, of great length, and terminating in a broad 

 fin, served as a rudder. The paddle-shaped fore- 

 limbs were probably used only as balancers. 



That these limbs are the result of specialisation 

 for the purpose of swimming there can be no 

 doubt, and it is equally certain that this peculiar 

 transfiguration can only have taken place after 

 they had ceased to be used as supports for the 

 body on dry land. The development of the 

 paddle-shaped fore-limb has resulted in many 

 profound structural changes in which only the 

 four fingers have escaped. Thus the upper arm 

 bone, or humerus, lost its characteristic shape, 



