DOUGLASS: THE TERTIARY OF MONTANA 211 
have a strong dip (20° or more) to the south and southwest. They are fine-grained 
with local bands and lenses of sand or small gravel. There are a few fair-sized peb- 
bles. The deposit is light gray, with a buff tint when viewed from a little distance. 
A large portion of the material is voleanic dust. All through the formation, at 
intervals, are nodules, which are arranged in bands. In places this nodular material 
forms strata. The nodules, as a rule, are hard, and in them most of the fossils were 
found. 
This interesting little area is situated north and a little east of Dillon, at a dis- 
tance of about sixteen miles. It is north of the Bighole River, and forms a small 
portion of the bench, or foothill country, of the southeastern slope of McCarty’s 
Mountain, where the bench borders the river valley. It is in Madison County. 
It is about a half-mile in length north and south and about one half that distance 
east and west. It is sharply distinguished, from the rocks which surround it 
on three sides, by its color and manner of weathering. On the north is an area 
of basalt perhaps about equal in area. his and the Tertiary deposits lie side by 
side at the same level, and there are fragments of basalt in the lower portion of the 
White River Beds. On the east, are the shales and sandstones of the Upper Creta- 
ceous. On the south, is the river valley, and on the west, sand and gravel benches, 
which are probably of later date than the Lower White River. 
The beds are imperfectly stratified —at least in some portions — though on the 
whole they are inclined to be rather massive. At a little distance the dip can be 
readily distinguished. As before stated, the greater portion of these beds is soft, and 
the product of their weathering is instructive, as it shows how material may be 
transported by water and deposited without regular assortment of material or 
stratification. The water which descends from this area at the time of heavy rains, 
or when snow is quickly melted, has formed a large alluvial cone immediately 
at the foot of the Tertiary hills. This is broadly spread out on the river bot- 
tem below, and by its peculiar color, its area can be readily distinguished at a 
distance. 
The following, so far as determined, are the genera found in these beds: Testudo, 
Helodermoides, Xenotherium, Peratheriwm, Ictops, Cylindrodon, Ischyromys, Palexolagus, 
Hyenodon, Limnenetes, Agriocherus, Titanothervwm, Colodon, Hyracodon, and Meso- 
hippus. Others are doubtful, or have not been sufficiently cleared from the matrix 
for certain determination. 
About two miles west of here is a small exposure of a little different character 
of strata. From here only two specimens were obtained, a Co/odon and an ap-~ 
parently new rodent. 
