154 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



some decided support to this hypothesis. According to 

 Osborn/ the White River Oligocene is very different from the 

 upper Oligocene of the John Day region and further shows 

 distinct Asiatic and European affinities indicating that the 

 Bering portal was closed during Lower Oligocene time. The 

 John Day Oligocene fauna, however, lacks European affinities, 

 thus indicating that the Bering portal was open at this time. 

 That a portion of the John Day is the land laid equivalent of 

 the Upper Marine Oligocene, the Acila gettysburgensis zone 

 is a probability. 



Comparison of the Lower Oligocene Fauna with the 

 Tejon Eocene Fauna 



The climate during the Tejon, Upper Eocene time on the 

 Pacific Coast was probably about the same as that of Lower 

 Oligocene time as indicated by faunal studies. Now some of 

 the striking things in the Tejon fauna are its general faunal 

 unity, the great range of many of its species, and the great 

 number of species composing it. These all appear to be func- 

 tions of a tropical climate, for when the recent tropical faunas 

 are studied the large number of genera and species is a charac- 

 teristic. Dall® has stated this as follows : "We may then con- 

 clude that that part of the average mollusk fauna which is cap- 

 able of leaving traces in the shape of fossils, under conditions 

 not greatly differing from those of the present day, if situated 

 in the Arctic or boreal region, would comprise about 250 

 species , in the cool temperate region about 400 species ; in the 

 warm temperate, about 500 species, and in the tropical region 

 not less than 600 species." 



A study of Caribbean Miocene (Upper Oligocene of Dall 

 and others) faunas reveals the fact that several highly orna- 

 mented gastropods persist to the Recent ; Turris alba Perry, for 

 example. Again, these Miocene faunas of the Caribbean ex- 

 hibit a remarkable unity both stratigraphically and geograph- 

 ically. Briefly, then, one of the characteristics of a tropical 

 fauna is the great range of many of its species. This subject 

 can not be discussed at length here but it is introduced to ex- 



' Osborn, H. F., Cenozoic Mammal Horizons of Western North America, U. S. 

 Geological Survey, Bull. 361, p. 66, 1909. 



• Dall, W. H., U. S. Geological Survey, Bull. 84, p. 27, 1892. 



