136 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



regarding their invariable presence in or absence from the two 

 groups before they can be accepted without reservation. 



Little account has been taken of the Odobenidae or walruses 

 in the present paper, but it may be mentioned that morphologically 

 they appear to be little more than specialized otariids, distinguish- 

 able chieflj^ by the enormous development of the upper canines 

 (which has been followed by necessary adjustments in the bones of 

 the skull) and compensating reduction in number of the remainder 

 of the teeth J as well as a change in their pattern to conform to 

 special food ; disappearance of the external ear, and a change in 

 the limbs, making these in some respects intermediate between those 

 of the Otariidae and Phocidae. There is no doubt whatever that 

 the relationship of the walruses is much nearer to the eared than to 

 the earless seal stem. 



Wortman (1894) believed that the Pinnipedia are derived from the 

 Oxyaenidae, a phylum of inadaptive creodonts. Matthew (1909) 

 has argued convincingly against this thesis, and ascribes ancestry to 

 the arctoid fissipeds, but Kellogg (1922) presents evidence which 

 apparently renders the latter as well as the former theory unlikely. 



Remains of unquestionable Pinnipedia of both otariid and phocid 

 affinities have been found from the Miocene, but from no deposits 

 of older age, and these remains are of pinnipeds which had already 

 reached a high degree of aquatic specialization. Hence it is certain 

 that this order diverged from terrestrial fissipeds at a very early 

 time. But until far more and considerably older remains of this 

 order than are now available are at hand, any attempt to allocate the 

 pinniped relationship and ancestry is too speculative for acceptance. 

 All that seems certain is that the pinniped precursor was of carnivore 

 stock, with probably some affinities with that large aggregation of 

 diverse predators known as the adaptive creodonts. In view of the 

 profound changes which had already taken place in pinnipeds of 

 the Miocene, the origin of this stock was " probably not later than 

 the Eocene " (Kellogg, 1922) and possibly earlier. 



There has been much conjecture regarding the derivation of the 

 pinniped families. Many investigators have considered that the 

 order is diphyletic or biserial, and some (as Mivart, 1885) have 

 favored the theory that the Otariidae are descended from an ursine, 

 and the Phocidae from a lutrme, ancestor, and have presented ana- 

 tomical data in support of such reasoning; but this is not convincing 

 and evidence of much weight may be marshaled against it. It is 

 hardly necessary to review this question in detail in the present con- 

 nection, but it has seemed to me rather unprofitable to consider seri- 

 ously the probable relationship of any family of pinnipeds with any 

 of existing fissipeds. Furthermore, the otariid stock is considered 



