194 THE STORY OF REPTILE LIFE. 



subjects of these transformations, probably in 

 all cases, began by haunting streams, then be 

 came amphibious, and finally drifted out to sea, 

 where the final stages of their evolution were 

 worked out. Thus has the sluggish tortoise 

 passed into the ocean-dwelling turtle; and 

 similarly, the scaly crocodiles and the ponderous 

 dinosaurs have furnished colonists to Neptune's 

 domain. 



The creatures we are now to discuss bear 

 further witness of this strange migration. 



Known as the Sauropterygia, the earliest 

 members of this group are represented by 

 certain primitive types, which dwelt probably 

 in the streams and estuaries of the old Triassic 

 rivers. Their descendants, strangely modified, 

 lived on until the Cretaceous. One of the best- 

 known of the ancestral forms, was a beast known 

 as Lariosaurus, a lizard-like animal some four 

 feet long. This represents the amphibious phase 

 of development, as is shown by the peculiar 

 form of the limbs, which are obviously more 

 adapted for swimming than walking. Indeed, 

 it is doubtful whether anything more dignified 

 than a shuffle was ever possible on land. We 

 have, indeed, in these legs, an intermediate 

 stage between the walking limbs of an earlier 

 period, and the swimming paddles which ulti- 

 mately succeeded them. Without describing 

 them in detail we may say that the hinder 

 pair were the longer, that the bones of tho 

 fore-arm and shank were moderately long, though 

 shorter than the arm and thigh, that the wrist 

 bones were small, and the hands and feet were 



