88 A BOOK OF~ WHALES 



way from that which we see in whales and seals. In 

 many fishes the hinder pair of limbs persists, but 

 is moved forwards so as to lie in the same straight 

 line, or thereabouts, with the anterior pairs of limbs. 

 In primitive fishes, on the other hand, such as Cera- 

 todus, the Australian mudfish, both limbs persist in 

 what we have to consider as the normal position. It 

 is exceedingly interesting to note that in the three 

 groups cited a practically similar result is obtained 

 in a totally different manner. 



In the last-mentioned character, therefore, as well 

 as in others which will be dealt with presently, the 

 seal tribe have pursued a different path towards the 

 complete adaptation to the aquatic life to that followed 

 by the whale tribe. But there is still a point remain- 

 ing, among what are practically external features, in 

 which the seals resemble to a certain extent the 

 whales. It is usual among terrestrial mammals for 

 the humerus to be longer, sometimes much longer, 

 than the radius. On the other hand, with the sole 

 exception of Inia, the whale's humerus is shorter 

 than the radius. Dr. Mivart* has owen some 



O 



measurements of these bones in representatives of 

 the three kinds of aquatic Carnivora, and his figures 

 are as follows : "In the common seal, Phoca vitulina, 

 the length of the humerus is 1 1 inches and that of 

 the radius the same ; in Otaria jubata, the Patagonian 

 sea-lion, the two bones measure respectively 23 and 

 24 inches. Finally, in the walrus the proportions are 

 30 and 23. It is curious to observe that the sea-lion 

 is the most whale-like of the three types." 



* "Notes on the Pinnipedia," Proc. Zool. Sac., 1885, p. 485. 



