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University of California Publications in Geology [Vol. 13 



necessary to have available for study all the previously described 

 fossil teeth and, besides, a much larger series than is now known. 

 The dentition of many of the most important forms, phylogenetically, 

 is totally unknown. 



The discovery of the phocid in the Santa Margarita beds failed 

 to give any evidence on this question because the cusps of the molari- 

 f orm teeth were broken off. The figures given by the various describers 

 of fossil pinnipeds indicate that there is nothing to disprove the 

 assumption that, the molars have evolved secondarily out of tuberculo- 

 sectorial molars. Professor Osborn 87 offers the following statement : 



As figured above, Phooa gichigensis exhibits a tooth analogous to that of the 

 Trieonodonta among the primitive marsupials, that is, with a main central and 

 two lateral cusps. We have seen that somewhat similar molars with several cusps 

 in a fore-and-aft line have evolved secondarily out of tuberculo-sectorial molars 

 in the case of the marsupial Thylaeinus and of the creodonts Mesonyx and 

 Hyaenodon. 



In conclusion, emphasis may be laid on the fact that while the 

 oldest otarids are from the west coast of North America and the 

 oldest odobenid from the Atlantic coast, the phocid types of North 

 America are too imperfectly known and are based on too fragmentary 

 material for one to determine their true relationships. 



In considering the various fossils assigned to the Phocidae it was 

 thought best to discuss them under the various stages to which they 

 belong. This method- makes possible a better understanding of the 

 sequence of the various forms in the different deposits. 



UPPER CRETACEOUS 

 One of the most unfortunate and questionable of all known fossil 

 remains attributed to the pinnipeds is the form described by Leidy 88 

 as Stenorh ynch us vet us. This name was based entirely on an outline 

 drawing made by T. A. Conrad of a tooth which was supposed to 

 have been found by Samuel A. Wetherill in the green sand of the 

 Delaware River valley near Burlington, New Jersey. This drawing 

 was reproduced by Leidy in his account and there is certainly a great 

 deal of resemblance to similar teeth of Lobodon earcinophaga. If we 

 are to believe this account of Leidy, and if the locality is not erroneous, 

 then it will be hard to dispute that one, at least, of the ancestors of 



* 7 Osborn, H. F., Evolution of mammalian molar teeth, pp. 143-144, fig. 103a. 

 New York, 1907. 



ss Leidy, J., Proc. Acad. Nat, Sci. Philadelphia, vol. 6, p. 377. 1853. 



