58 THE MAMMALIA OF THE DEEP KIVER BEDS. 



p. 660) I gave preliminary definitions of the new genera and species contained in the 

 collections made by the Princeton party. 



Now that this collection has been worked over and can be compared with Prof. 

 Cope's material from the same locality, some definite statements may be made with 

 regard to the geological and palaxmtological relations of the Deep River beds. So far 

 as the stratigraphy is concerned, there is little to add to the account of Grinnell and 

 Dana, except in one particular. The statements of these authors seem to imply that 

 the two sets of beds are conformable throughout, but there is strong evidence which 

 goes to show that this is not the case. In the first place, there is a marked litholog- 

 ical contrast between the two series, the lower being very hard and the upper, for the 

 most part, incoherent sands, though nodules of harder material have, in many cases, 

 formed around the bones. The general character of the lower beds is very much like 

 that of the older Miocene, the "White River or John Day, while the upper are more 

 like the Loup Fork. Though both sets of strata are generally horizontal, with local 

 exceptions, the ujaper beds appear to rest upon an eroded surface of the underlying 

 strata. Thus, at one point, the older beds, as exposed in a line of buttes — appar- 

 ently, at least — rise higher than an exposure of the newer strata across the ravine 

 from the first exposure. In the absence of instruments, this point could not be 

 determined quite certainly, but it is very probable. Towards the north and east the 

 upper beds appear to extend beyond the lower and to produce an uncomformity by 

 overlap. Finally, the fossil contents of the two series of strata are very strikingly 

 different, not a single species of mammal and not more than two genera are common 

 to the two, and those genera range from the John Day into the upper Loup Fork. 

 Such radical and sudden changes are hardly to be explained on the hypothesis of 

 migration, and point to a considerable hiatus between the times of deposition of the 

 two sets of strata. 



The following species of mammals were found in the lower beds : Cynodesmus 

 tliooides Scott, Steneqfiber montanus Scott, Ccenopns sp., Miohippus annedens? Marsh, 

 M. ancepsf Marsh, M. (AncMtherium) equiceps f Cope, Mesoreodon cJielonyx Scott, 

 M. intermedins Scott, Poebrotherium sp., Hypertragulus calcaratus Cope. This list 

 appears to be a scanty one, but this is explained by the fact that the exposures which 

 yielded well-preserved fossils are very limited in extent, a few acres at most, and 

 when we compare them with the vast regions over which collections from the other 

 Tertiary formations have been gathered, the disproportion will not seem so striking. 

 Indeed, I know of very few spots of equal extent which have yielded so large a 

 number of individuals and species. The facies of this fauna is undeniably that of 

 the John Day Miocene. All of the genera but two, and several of the species, occxir 



