ILLUSTRATIONS 



MOUKii PAGE 



temporal); quj, quadratojugal; sur, surangular; an, 

 angular; pospl, postsplenial; spl, splenial. 



Figures 48-52 give excellent examples of " Williston's 

 law" of the progressive elimination of skull elements 

 in passing from fish to man. 



53. — Evolution of the Under Side of the Skull 85 



I. Lobe-finned fish (Eusthenopteron) , Devonian. 

 (After Bryant, Watson.) 



II. Primitive amphibian (Baphetes), Carboniferous. 

 (After Watson.) 



III. Primitive cotylosaurian reptile {Seymouria), 

 Permo-Carboniferous. (After Watson.) 



IV. Advanced cotylosaurian reptile (Captorhinus), 

 Permo-Carboniferous. (Original.) 



V. Gorgonopsian reptile (Scymnognathus), Per- 

 mian. (After Watson.) 



VI. Advanced mammal-like reptile {Cynognathus), 

 Triassic. (Mainly after Watson.) 



VII. Marsupial mammal {Thylacinus), Recent. 

 (Original.) 



VIII. Eocene lemuroid primate {Adapts). (After 

 Stehlin.) 



IX. Anthropoid (female chimpanzee). (Original.) 



X. Man (Australian aboriginal). (Original.) 

 Abbreviations: pmx, premaxilla; mx, maxilla; ju, 



jugal; quj, quadratojugal; qu, quadrate; nar, internal 

 naris; pv, prevomer; pi, palatine; ecipt, ectopterygoid; 

 epipt, epipterygoid; pt, pterygoid; pas, parasphenoid ( = 

 vomer, »); bs, basisphenoid; bo, basioccipital; exo, exocci- 

 pital; ops, opisthotic; mst, mastoid portion of periotic; 

 bul, auditory bulla; sq, squamosal; alsp, alisphenoid. 



54. — Anatomy of the Lancelet (Amphioxus), the 

 Most Primitive Living Chordate (Pre- 

 vertebrate) Animal .... 92 



(After Delage and Herouard.) 



A. Entire animal, seen as a semi-transparent object. 



B. Longitudinal section. 



xxiv 



