28 ' STUDIES IN GEOLOGY, No. 3 



The following table will show readily the distribution of 

 affinities for the total fauna. The percentages represent 

 those of species either occurring elsewhere or having close 

 relatives elsewhere at the horizons noted. 



Restricted to Burdigalian . . . .' 43% 



Occurring in Burdigalian 71% 



Restricted to Helvetian 7% 



Tortonian and later 11% 



Oligocene (chiefly Aquitanian) 10% 



Eocene $% 



It is thus clear, although these figures are really not the 

 most efficient medium of expression, that the fauna is un- 

 mistakably Burdigalian in age. Since 87 of the 101 species 

 are peculiar to the Zorritos formation it is practically nec- 

 essary in attempts at expressing analysis to consider close 

 affinities together with identical occurrences, and inasmuch 

 as such affinities as have been indicated are close enough to 

 warrant such action, the two are not separated in discussions 

 of totals. 



This determination confirms Grzybowski's statement of 

 the age of his collections from the same horizons, and it is 

 worthy of note that he obtained his results through compar- 

 ison with European species, almost to the exclusion of 

 others, at a time when the geology of the Panamanian- 

 Antillean region was little known. He did not place his 

 fossils definitely in the Burdigalian, but stated that they 

 were of Lower Miocene age. A later determination of the 

 age of the Variegated formation, by Berry, 19 depends on 

 fossil plants for its conclusion, and agrees with Grzybowski's 

 results in calling the beds Burdigalian. The results of these 

 observations, diverse in manner of treatment, agree with 

 satisfying precision. 



Twenty-two of the 101 species are either closely related to 

 or identical with Gatun species; 29 with Santo Domingan 



19 Proc. U. S. Nat. Mus., vol. 55, No. 2270, pp. 283-284, 1919. 



