DOUGLASS : THE TERTIARY OF MONTANA 209 
PARTY II. LEPTICTID® OF THE LOWER WHITE RIVER BEDS. 
Nearly sixty years ago, a man who resided at one of the posts of the St. Louis 
Fur Company, on the Missouri River, sent to Dr. Hiram Prout, of St. Louis, a frag- 
ment of the lower jaw of a large and unknown animal. It was found in the Bad 
Lands of White River, about sixty miles east of the Black Hills. Dr. Prout de- 
scribed and figured this jaw—the last molar of which was complete —in the 
American Journal of Science (1847). From the resemblance of the last lower molar 
to that of Palxothervwm of the European Tertiary, it was supposed to belong to that 
genus. This is what is now known as Titanotheriwm, and it was the first mammalian 
fossil described from the White River Beds of the West. Since then all the parts 
of the skeleton and hundreds of skulls of this animal have been found, and all from 
the lower horizon of the White River. Besides this, skulls and skeletons of the large 
EHlotheriwm, Metamynodon, Trigonias, and other Rhinoceroses have been obtained ; but 
aside from these, previous to the discoveries in Montana, almost nothing was known 
of the immediate precursors of the abundant and varied fauna, which had been so 
well preserved in the overlying Oreodon Beds. 
In the year 1900 the present writer discovered, in three localities in Montana, 
remains of smaller mammals associated with Titanotheriwm. Of these about a dozen 
species were described.' The types were teeth, jaws, and portions of skulls. Among 
these, only one skull was nearly complete. 
The American Museum Expedition to Western Montana in 1902, discovered 
nearly a dozen more species. ‘These were all represented by jaw fragments with 
teeth. Twenty-three species and six new genera had now been described, principally 
from teeth and jaws. They were of much interest, as they represented a new 
fauna, and gave a better basis for comparison of the mammals of the Titanotherium 
Beds with those of the overlying Oreodon Beds. They were mostly small animals 
— marsupials, insectivores, rodents, and small ungulates. 
In the summer of 1903, the Carnegie Museum Expedition in charge of the present 
writer, discovered a locality on the Bighole River, near McCarty’s Mountain, north 
of Dillon, in Montana, which yielded far more complete specimens of this smaller 
fauna. In this collection there are many skulls of smaller animals — some almost 
complete —with portions of skeletons, also jaws with fuller teeth series, of larger 
animals. 
These specimens, so far as they have been studied, do not appear to lessen the 
hiatus between the Titanotherium and Oreodon Beds, or the greater one between the 
former and the Uinta. 
1 Trans. Am. Philos. Soc. N. S., Vol. XX., pp. 237-279. Ann. Carnegie Mus., Vol. II., No. 2, pp. 145-150. 
