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by King, probably represent a faunal stage comprised within the 

 latter half of the Miocene. The fauna of eastern Oregon referred to 

 the Pliocene by Marsh is largely that of the Mascall, which is Middle 

 Miocene. The Niobrara fauna of the Great Plains region, with which 

 the Bone Valley collection may really have some affinity, as suggested 

 by King, is generally considered as Upper Miocene. The palaeonto- 

 logic basis for age determination of the "Humboldt Pliocene"' of 

 King's Shoshone Lake of the Middle Basin area seems, then, to indicate 

 Miocene at what may be considered a typical locality of these beds. 

 Whether other evidence may indicate that a large portion of the 

 deposits mapped as Pliocene by King really represents that period 

 remains to be demonstrated. It seems probable that a considerable 

 part of these deposits may be Miocene. Other portions are probably 

 Pleistocene. The occurrence at Ricardo, on the western border of the 

 Great Basin, of a series of beds representing a faunal and stratigraphie 

 stage which is distinctly pre-Pleistocene, is certainly much later 

 than the Mohave Upper Miocene, and presumably represents early 

 Pliocene, shows that accumulation was taking place in the Basin 

 Region in or near Pliocene time. The difficulties encountered in age 

 determination or correlation of widely separated exposures of Ter- 

 tiary strata in the Great Basin make one hesitate to accept much, if 

 any, of the Pliocene of King as really representing the Ricardo stage. 



The occurrence of mammal remains at the McKnight locality not 

 only changes our views regarding the Pliocene of the Great Basin, but 

 also modifies to some extent the views on distribution of the Miocene 

 originating with King. According to the report of the Fortieth Par- 

 allel Survey, Miocene beds are confined to a region west of 117° west 

 longitude, while Eocene does not range west of the 116th meridian. 

 The McKnight locality, situated near 115° 30', is considerably east 

 of King's most easterly Miocene and is east of the most westerly 

 Eocene exposures. A question is naturally raised regarding the 

 relative age of the Tertiary at the McKnight locality and the 

 beds referred to as typical Miocene of the Truckee beds farther west. 

 The Truckee as discussed by King was determined as Miocene almost 

 solely on its lithologic resemblance to the John Day beds of Oregon. 

 The only palaeontologic evidence of contemporaneity of the Truckee 

 with the John Day consisted of a single rhinoceros tooth referred to 

 Rhinoceros pacificus, of the John Day region. This specimen is not 

 available for comparison. Within the past few weeks Mr. John P. 

 Buwalda of the University of California, in examining a section of 



