Vol. VII] DICKERSON— CLIMATE AND OLIGOCENE FAUNAS 165 



plain the Tejon faunal conditions. That Tejon time was not 

 short is indicated by great thicknesses of beds bearing its 

 characteristic fauna, by coal beds at different horizons, and by 

 certain faunal conditions which can not be stated briefly. 



Since the climatic conditions of the Tejon and Lower Oligo- 

 cene were much the same, several species common to the two 

 might be expected. Weaver reports Brachysphingus clarki, 

 Leda uvasana, Crassatellites washingtoniana, Exilia dicker- 

 soni, and Hemifusus washingtonianus, as Tejon forms which 

 also occur in the Molopophorus lincolnensis zone. This is a 

 very small number and, moreover, further collecting has not 

 increased it. It appears probable that a great interval of 

 erosion occurred between the beds bearing the Upper Eocene 

 and Lower Oligocene faunas and that the Tejon species fin- 

 ished their life course during the time now represented in the 

 rocks by an unconformable contact yet to be discovered.' 



With a subtropical climate during Lower Oligocene (Molo- 

 pophorus lincolnensis and Turritella porterensis zones) time, 

 a faunal character similar to that of the Tejon is to be ex- 

 pected. Hence it may be predicted with a fair degree of 

 safety that the number of species composing the Lower Oligo- 

 cene fauna will be large, the ranges of many of the species 

 very great both stratigraphically and geographically, and that 

 additional collecting will increase the similarity between the 

 Molopophorus lincolnensis and the Turritella porterensis 

 zones. 



Conclusions 



(1). The fauna described in this paper represents a lower 

 facies of the Molopophorus lincolnensis zone of Weaver. 



(2) The climatic conditions during its deposition were sub- 

 tropical. 



(3). The Molopophorus lincolnensis and the Turritella 

 porterensis zones have as yet been but imperfectly described 

 and their unity is much greater than the temperate fauna of 

 the Acila gettysburgensis zone of the Upper Oligocene. 



(4). The Acila gettysburgensis zone is possibly the corre- 

 lative of a portion of the Upper John Day Oligocene. 



* Since this was written, Professor C. E. Weaver has announced the occurrence 

 of unconformities in several places in Washington. 



