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 vertebrse 
that suggest a relationship with the Labyrinthodonts, such as 
Archsegosaurus (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 
