THE GREAT FISH-LIZARDS 73 



life-history of these ancient monsters. Palaeontologists have good 

 reason to believe that they were descended from some early form 

 of land reptile. If so, they show that whales are not the first 

 land animals that have gone back to the sea, from which so many 

 forms of life have taken their rise. 



During the long Mesozoic period fish-lizards played the part 

 that whales now play in the economy of the world; and they 

 resembled the latter, not only in general shape, but in the situa- 

 tion of the nostrils (near the eye), and in their teeth and long 

 jaws. But these curious resemblances must not be interpreted to 

 mean that whales and fish-lizards are related to each other. They 

 only show that similar modes of life tend to produce artificial 

 resemblances just as some whales, in their turn, show a superficial 

 resemblance to fishes (see p. 68). 



With regard to the particular form of reptile from which the 

 fish-lizard may have been derived, no certain conclusion has at 

 present been arrived at. This is chiefly from want of fuller 

 knowledge of early forms, such as may have existed in the previous 

 periods known as the Carboniferous and Trias (see Appendix I.). 

 But there are certain features in the skulls, teeth, and vertebrae 

 that suggest a relationship with the Labyrinthodonts, such as 

 Archaegosaurus (see p. 96), or primaeval salamanders that flourished 

 during the above periods, or at least from amphibians more or 

 less closely allied to them. They cannot by any possibility be 

 regarded as modified fishes ; for fishes have gills instead of lungs. 

 Professor Merriam has found in the Triassic strata of California 

 some of the links between some old land-reptiles and the fish- 

 lizards ; but at present no early marine ancestors have come to 

 light. 



The fish-lizards played their part, and played it admirably ; but 

 their days were numbered, and the place they occupied has since 



