1922] Kellogg: Pinnipeds from Miocene and Pleistocene Deposits 99 



their subsequent modification for a crushing function, in the enormous 

 development of the upper canines as tusks, and finally in the loss of 

 most of the hair and its replacement by blubber. 



The Otariidae, taking all the evidence into consideration, appear 

 to be the least adapted to a pelagic life or at least have adopted such 

 a life at a much later period than either the Phocidae or Odobenidae. 

 One writer, Sclater, 198 misled by the lack of authentic fossil otarids, 

 went so far as to state that Otaria (—Eumetopias) was originally an 

 Antarctic form, the present forms on the west coast of North America 

 being offshoots of that stock. 



In the matter of cranial changes it is difficult to say with any 

 degree of precision what has actually occurred. The form, Allodes- 

 •mus, throws some light on these changes. There are certain cranial 

 changes in the configuration of the skull with evolution in the car- 

 nivora as was shown by Dr. Matthew. 199 He pointed out that the high 

 sagittal and occipital crests become reduced with the lateral expansion 

 of the parietals and squamosals. With the increase in area for attach- 

 ment of temporal muscles of the lower jaws the need of such additional 

 supports is lessened. This change can be best illustrated by a com- 

 parison of Arctocephalus cmstralis with Callotaria alascana. The 

 former possesses a high sagittal crest, small brain case with long inter- 

 orbital region, but with orbit far forward. The latter has a marked 

 lateral expansion of the parietals, no sagittal crests except in old 

 adults, a relatively large brain case, and a short broad interorbital 

 region. This enlargement of the orbit may be due to an increase in 

 the size of the eye to adapt the animal for under water vision, parallel- 

 ing conditions in this respect observed by Professor John C. Mer- 

 riam 200 and others in the ichthyosaurs. 



An attempt to account for the evolution of the Pinnipedia on the 

 basis of successive adaptive changes to an aquatic mode of life will 

 probably be critized by experimentalists. They have endeavored to 

 show that such characters would not be inherited and have brought 

 forward much evidence to support their contention. But no matter 

 how we may try to explain these modifications in the various members 

 of the Pinnipedia, it is evident that changes in food and habits have 



198 Sclater, P. L., On the distribution of marine mammals. Proc. Zool. Soe. 

 London, p. 350. 1897. 



168 Matthew, W. D., The earnivora and inseetivora of the Bridger Basin, Middle 

 Eocene. Mem. Am. Mus. Nat Hist., vol. 9, pt, 6, p. 312. 1909. 



200 Merriam, J. C, Triassic ichthyosauxia, with special reference to the Amer- 

 ican forms. Mem. Univ. Calif., vol. 1, p. 74. 1908. 



