120 PROCEEDINGS OF THE ACADEMY OP 



Drs. Evans and Shumard, belong to the vertebrata, and are consequently oat 

 of our line of investigation. 



During the later explorations in that region, facts were observed tending 

 to throw doubt upon the conclusion that these formations belong to the 

 Eocene epoch. Among other facts of this nature, we would mention that a 

 friable sandstone seen crowning some of the hills near Moreau River, in which 

 specimens of a Cyrena described in one of our former papers (6'. Moreauensis) 

 and Ostrea sublrigonalis (E. & S.,) were found associated with large bones sup- 

 posed to be those of Titanotherium^ and which bed we had regarded as probably 

 a distant outlier of the White river formations, was found to be the same as 

 the lowest bed of the Great Lignite basin extending far to the northward. 



Now as the Tilanotherium bed of the White river basin is the oldest member of 

 that series, it must be manifest if the species of the Tilanotherium occurring 

 Rt these two localities are really identical, we must either admit the remains 

 of that animal had a great vertical range, which is not the case in the White 

 River deposits, or suppose these two basins are nearly or quite exactly on 

 a parallel. 



In addition to the foregoing, some Miocene deposits seen crowning the sum- 

 mits of hills on the east side of the Missouri, near the mouth of White River, 

 were traced by a series of outliers up the valley of the latter stream, to where 

 they were found to pass into the upper part of the well known Mauvaises Terres, 

 extending towards the sources of that stream, and which have furnished so many 

 interesting vertebrate remains. 



After comparing and discussing these facts we suspected that the whole of 

 the White River basin might be more properly of Miocene than Eocene age, and 

 upon glancing over D'Orbigny's tables showing the vertical range of the 

 various genera of fossil vertebrata, and consulting Picktets Traite de Palceon- 

 tologie, we observed that several of the old genera to which Dr. Leidy refers the 

 White River Mammalia are regarded in the Old World as characteristic of 

 the Miocene epoch. These enquiries, however, being out of our line of 

 investigation, we wrote Prof. Leidy, the distinguished comparative anatomist of 

 Philadelphia, who has so ably investigated all the vertebrate remains hithert<^> 

 brought from Nebraska, stating our doubts and suspicions respecting the age of 

 these deposits, and requesting him to examine very carefully the large water- 

 worn bones from Moreau and Grand Rivers, occurring in what we knew to be 

 the lowest bed of the Lignite basin, and to inform us if he was quite satisfied 

 they are identical with Titanotherium Prouti ; also making enquiries respecting 

 the Eocene or Aliocene affinities of the various new genera of Mammalia 

 described from the Bad Lands of White River by him. Since that time we were 

 much gratified to learn from Prof. Leidy that as much as three or four weeks 

 previous to the reception of our letter, he had arrived at the conclusion, from 

 purely palasontological evidence, that the White River deposits must belong 1« 

 the Miocene epoch. 



Prof. Leidy has presented his views in regard to the Miocene affinities of the 

 vertebrata from the White River formations, in some interesting remarks ac- 

 companying a complete catalogue of all the organic remains described by him 

 from Nebraska, recently read before the Academy ; a copy of which he has 

 kindly placed in our hands in advance of the regular issue of the Proceedings. 

 From these remarks we extract the following in reference to the fossils from 

 the Wliite River basin : 



" Oreodon, Agriochoerus Pcebroiherium, Leptomeryx, Leptauchenia, Protom&ryx^ 

 Merycodus Titanotherium, Leptochaerus, Hyracodon, Merychippus, Ischyromys, Pa- 

 Imolagits, Eumys, Dinictis and Leptarctus, are peculiar, extinct mammalian genera, 

 from the Tertiary formations of Nebraska, which have heretofore been generally 

 viewed as belonging to the Eocene period, but from their affinities, the asso- 

 ciated genera, and the absence of others so common in the Eocene deposits of 

 Europe, I suspect rather belong to the Miocene period. The first seven genera 

 above mentioned are true ruminants, with teeth constructed upon the same type 



[May, 



