PALEONTOLOGY ZORRITOS FORMATION 31 



13 species appear to have well-defined lower Miocene affin- 

 ities, and five of them are apparently of Chilean Miocene 

 types. It is the belief of the writer that the Variegated beds 

 will be shown to contain many more species in common 

 with the Upper and Lower Zorritos formations than are 

 now apparent. 



Lower Zorritos Fauna: This fauna presents the most 

 strongly peculiar aspect of all. In addition to the fact, al- 

 ready noted, that it shows very strongly centralized affinities, 

 it has a facies more distinctly peculiar than has either of 

 the other two faunas. The Gatun-Cercado elements are 

 certainly predominant, and the age of the fauna is certainly 

 Burdigalien, at least in the sense of the American strati- 

 graphers. Over half of the Lower Zorritos species are 

 closely related to species restricted to* the Burdigalien, and 

 approximately eighty per cent to species occurring in the 

 Burdigalien. The affinities of other elements in the fauna 

 may be seen readily in the tables, plates 2, 3 and 4. 



Nelson's Collection: The collection described by Nelson 

 contains a number of species which do not occur in the 

 Hopkins collection. Inasmuch as Messrs. Larkin and 

 Bradley, the collectors, stated that the specimens came from 

 the direct vicinity of Zorritos, in which locality the Zorritos 

 and Heath formations are the only ones exposed, and since 

 the general facies of Nelson's fossils indicates a common 

 origin, they have been assumed to come from the Zorritos 

 formation. It is unfortunate that they have not been located 

 within the limits of that unit, but when considered with the 

 fauna as a whole they contribute interesting additional evi- 

 dence of the Burdigalian age of the beds. Approximately 

 forty per cent of the species have restricted Burdigalian 

 affinities. 



The exact relationships of the species in this group may be 

 seen in the accompanying table, where they are listed as 

 "Undifferentiated." 



