244 University of California Publications in Geology [Vol- 7 



Explorations in California," (U. S. Pac. R. R. Surv. for 1853, pp. 

 313-316, pi. 1). Since 1907 a review of these papers of Agassiz 

 and of Jordan has been published by Maurice Leriche of Lille. It 

 is entitled "Observations sur les Squales Neogenes de la Cali- 

 fornie" and published in the Annales de la Societe Geologique du 

 Nord (tome xxxvii, p. 302. December, 1908). Tbis paper is 

 based chiefly on the descriptions and figures published by the 

 senior author in 1907. It consists mainly of a comparison of 

 these California species with those of the same horizon in Europe. 

 Leriche regards most of the species as identical with the 

 European species. It may be freely admitted that in several 

 eases no differences can be made out from the teeth alone. In 

 several genera of sharks, the dentition is the same in all the 

 several species. But to unite nominal species from opposite 

 sides of the globe has also its difficulties. In most cases, the 

 existing species of shark are largely localized, and it must have 

 been so in the Miocene period. There are reasons of convenience 

 for having a different set of specific names in each distinct faunal 

 area. At the best, the substitution of Leriche 's names for those 

 of Agassiz in California is the exchange of one doubtful opinion 

 for another. If we trust to teeth alone certain species will 

 appear to have not only a cosmopolitan distribution but an 

 abnormally wide range in geologic time. As the wide-ranging 

 forms among the existing sharks have been studied more care- 

 fully, these have been split up into distinct species showing 

 more or less definite localized differences. AVhile no one can be 

 sure that some of these sharks were not fully identical with 

 European forms, we know that some of them are not so. We 

 know also that the Miocene fauna of California is in general 

 wholly different from that of Europe and also from that of the 

 eastern portions of the United States. Where a California 

 species has received a distinctive name we may provisionally 

 allow that name to stand, even if no known characters separate 

 the teeth in question from those of their European analogies. 



Still later, several authors (Ameghino, Leriche, Woodward, 

 Gaudry, Tournouer, Priem) have written on the Tertiary fishes 

 of Patagonia, in which region occur a series of sharks, the teeth 

 of which show a very strong resemblance to the species known 



