ICHTHYOSAURIA 



"3 



ago that they had descended directly from fishes. But this belief 

 has been quite abandoned by all, not only because the recent dis- 

 coveries of the earlier ichthyosaurs have demonstrated a positive 

 increase in the aquatic adaptations of the later forms, but also 



Fig. S3. — Baptanodon {Ophthalmosaurus). SkvJl from the side, from above, and 

 from below (after Gilmore): ang, angular; bs, basisphenoid; d, dentary; fr, frontal; 

 /", jugal; la, lacrimal; mx, maxiUa; na, nasal; oc, occipital condyle; p, palatine; pa, 

 parietal; pm, premaxilla; po, postorbital; ps, parasphenoid; pt, pterygoid; pf, pre- 

 frontal; sa, surangular; sp, splenial; sq, squamosal; st, supratemporal; q, quadrate; 

 qj, quadratojugal. 



because a double origin of any type of animal life is quite out of 

 accord with all known facts and principles of paleontology. It is 

 quite possible for animals, in becoming adapted to peculiar environ- 

 mental and food conditions, to acquire certain resemblances to 



