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University of California Publications in Geology [Vol. 13 



Since the environmental factor is nearly constant, aquatic forms, 

 especially the higher mammals, should show the nature and direction 

 of this variation. It can hardly be disputed that terrestrial mammals 

 which later become aquatic will betray somewhere in their make-up 

 structural peculiarities which will show, in turn, the nature of the 

 modifications that are induced by the changing environment. In such 

 forms one should be able by a study of the recent and the fossil 

 members to trace their evolution with a fair degree of precision. We 

 are hampered in this case by the fact that in the Pinnipedia many 

 of the important links in the paleontologic evidence are missing. 



ANCESTRAL OTARI1DAE 



Although a considerable number of genera belonging to the families 

 Phoeidae and Odobenidae have been made known in various paleon- 

 tologic studies, yet very few of the earlier types of the Otariidae have 

 been discovered. On the other hand, all authentic fossil otarids are 

 based on portions of a skull at least, while the skulls of the fossil 

 Phoeidae, with the exception of one or two forms, are unknown. 



One readily observes that some of the teeth, from various deposits 

 in France, which have formed the basis for new forms of supposed 

 otarids arc quite like similar teeth possessed today by Eumciopias 

 and Arctocephalus. One finds it very difficult, however, to allocate 

 these isolated teeth with any known mammal. Until the skull or parts 

 of the skeleton are known the true relationships of the animals to 

 which these teeth belonged will remain in doubt. A thorough explora- 

 tion of some of these deposits in France and elsewhere should reveal 

 much interesting material. Corroborative evidence in the way of 

 additional material for the tooth described as Palaeotaria henriettae 

 by Leriche 61 will be extremely interesting. This tooth was found 

 in deposits, assigned to the Tongrien period, in the neighborhood of 

 Rennes, France, and was considered by Leriche to be the oldest known 

 pinniped. No other pinnipeds are known from the Oligocene with 

 the possible exception of the dubious phocid found associated with 

 Squalodon and Halytherium (= Crassitherium) in the Rupelian clay 

 at Elsloo, a town north of Maestricht, in the province of Limburg, 

 Holland. 



ci Leriche, M., Sur le plus ancien reste eonnu de 1 'Ordre des Pinnipedes. 

 Annates Soe. Geol. du Nord, Lille, vol. 39, pp. 369-370, fig. 1. 1910. 



