1910] Merriam: Mammalian Remains from Ironside, Oregon 131 



to Equus, and there can be no doubt that the fauna at Ironside is not 

 contemporaneous with that portion of the Idaho formation from which 

 Lindgren's Idaho fauna was obtained. 



At the present time some of the important problems in Tertiary 

 geology and palaeontology of the Great Basin region depend upon an 

 understanding of relationships between the John Day section and that 

 of the Idaho region. By reason of its geographic situation the occur- 

 rence of mammal remains at Ironside may ultimately be of large 

 service in the work of determining the time-relations between the 

 Idaho sequence of faunas and the sequence of the John Day region. 

 The Ironside locality is so situated that mapping of the region will 

 make possible a determination of the stratigraphie relations of the 

 sediments to the formations of the Snake River region of Idaho. Large 

 exposures of sedimentary formations extend with few apparent inter- 

 ruptions from Ironside along Willow Creek and Malheur River to the 

 type areas of the Idaho and Payette formations of the Snake River 

 Valley. Some of these exposures presumably represent the Idaho 

 formation, but it is not improbable that several formations or several 

 stages of the later Tertiary are represented. The Ironside locality is 

 also situated near the John Day Valley, in which there is represented 

 the best stratigraphie section and the best palaeontologic sequence 

 known as yet in the Great Basin province. It is probable that further 

 palaeontologic and geologic studies will make it possible for us to 

 understand the relation between the beds at Ironside and the John 

 Day section. There is further the possibility that we may be able to 

 determine the relation of the formation at Ironside to a great series 

 of Tertiary deposits on the south side of the Blue Mountains, immedi- 

 ately to the south of the John Day Valley. The exposures on the 

 south side of the Blue Mountains presumably represent a large part 

 of the sequence of formations and faunas known within the John 

 Day Valley. 



HIPPARION ANTHONYI, n.sp. 



Type specimen a second lower premolar, no. 22351, from Tertiary beds 

 exposed three-fourths of a mile south of Ironside, Malheur County, Oregon. 



The species is represented by a single tooth presented by A. W. Anthony of 

 Ironside, Oregon. The horizon at which this specimen was found is presumed 

 to be early Pliocene or latest Miocene. 



Crown of medium height, narrow transversely. Enamel pattern showing 

 uncommonly strong secondary plications. Several very strong secondary 

 plications forming a sheaf of projecting folds on anterior side of hypoeonid. 



Specimen 22351 (figs, la to lc) differs from Merychippus and 

 PUohippus in its greater relative size and stage of advance of the 



