NATURAL SCIENCES OF PHILADELPHIA. 121 



a3 those of living ruminants ; a type which is not found in the Tertiary deposit.^ 

 of Europe and Asia, earlier than the Miocene period. 



Entelodon Palceochcerus, Rhinoceros, llipparion, Sleneojiber, Amphicyon, and Ma- 

 ckairodus, are common to the Nebraska Tertiary deposits and to the Miocene and 

 later Tertiary deposits of Europe ; and they have not been found in the Eocene 

 formations of the latter continent. 



Of tlie genera Anchitherium, ITyopotamus and Hymnodon species are found 

 common to the Nebraska Tertiary deposits and the European Eocene and Mio- 

 cene deposits. 



Remains of P.rloiolherium, Anoplothrrium and Lophiodon, so common in the 

 Eocene formations of Europe, are entirely absent from the Nebraska Tertiary 

 formations. 



Titanotherium of Nebraska most nearly approaches the Miocene Chaliocotherium 

 of Europe and Asia. 



The rodents hchyromys, -Palmolagus and Eumys, most closely approach the 

 Arctomyx, Lrpus and Muh of European Miocene and later deposits. 



Very numerous remains of Tcstudo are found in association with the Nebraska 

 Tertiary mammals ; and extinct species of the same genus belong generally to 

 the Miocene and later deposits of Europe." 



From all the foregoing facts, the Miocene age of these White River formations 

 may, we think, be regarded as established, both by paloeontological and strati- 

 graphical evidence. There are, however, many points of interest in regard to 

 the exact parallelism of these deposits with those of the Great Lignite basin, 

 yet unsettled. If it be true that the large bones previously referred to in both 

 basins, do really belong to the same species of animal, it would seem, from the 

 fact that they occur in the lowest bed of each, that the two basins are not 

 merely both Miocene, but exactly on a parallel. If so, it is very difficult to 

 account for the fact that, out of the numerous organic remains hitherto found 

 in the two deposits, not a single species, excepting Titanotherium Prouti* should 

 be common to both ; especially when we bear in mind the fact that the two 

 basins approach to within forty or fifty miles of each other. 



It is true, several of the Mollusca occurring in the bone bed, or lowest stratum 

 of the Lignite basin, belong to genera only found in salt or brackish waters, 

 and that none but terrestrial and fresh-water types have yet been found in any 

 part of the White River deposits ; thus indicating that one is a lacustrine for- 

 mation, and the other an estuary deposits ; conditions, it is true, not very favor- 

 able to the existence of the same species of mollusca, but hardly sufficient, we 

 think, to account for the fact that all the shells hitherto collected from the lig- 

 nite formations are not merely different species from those described by Drs. 

 Evans and Shumard, from the White River beds, but belong to slightly different 

 types. 



The entire absence, so far as we yet know, of the fossil plants occurring in 

 such great abundance in the Lignite formations, in those of the White River 

 basin, is also worthy of note ; while the lithological differences between the two 

 deposits are well marked. The latter point of difference will be more obvious 

 on comparing the following section of the Lignite formations taken by one of 

 U3,f at a locality thirteen miles above Fort Clark, on the right bank of the Mis- 

 souri, with the section of the Bad Lands of White River, as given by Dr. Evans 

 in Dr. Owen's Report, page 200. 



* Since the«e remarks were communicated to the Academy, we have been informed by 

 Prof. Leidy that he now rather suspects the large bones here alluded to belong to a huge 

 Dinosanrian described by him from these beds, under the name of Thespesius. 

 He further states that he had merely referred them provisionally lo Titanotherium Prouti. 

 from their great size, as none of them he has yet seen show even the articulating ex- 

 tremities. 



t Dr. Hayden. 



1857.] 



