EXISTING ORGANISMS— ANATOMY 



71 



the chondrocranium, from which develops the occipital bone, 

 Laterad and ventrad other bones occur, but these are primarily 

 visceral in their associations (Figs. 36 and 46). 



Above the Amphibia. In the reptiles, birds and mammals the 

 same essential parts and relationships persist, with some slight 



./-Ai-^ 



Fig. 47. — Morphology of ribs, a, ganoid fish; b, dipnoid fi.sh; c, teleost fish; 

 d, shark; e, Polypterus, a special case among ganoids; f, urodele a^nphibian. 

 In the first three the condition in trunk (left) and tail (right) is given. In 

 all figures the "fish rib" is striped and the true rib is black. (From Wilder's 

 History of the Human Body, after Wiedersheim, with the permission of 

 Mrs. H. H. Wilder and Henry Holt and Company.) 



variation in the accessory frontals and in the proportionate sizes 

 of the various bones. 



The Human Skull. The skull of man differs in a few conspicuous 

 points, although it is in general similar. The nasals persist as 



