Progress in Mammalian Palaeontology. — Osborn. 229 
Thus the degree of zoological kinship of the continents 
may be expressed as follows : 
1. Close kinship of North America, Asia and Europe 
(= Holarctica), having all pre-Miocene Orders 
in common, and separated only by the indepen- 
dent radiation of certain families. 
2. Separation of Africa as a pre-Miocene centre of at 
least three orders not found in Holarctica. 
3. Strong separation of South America from the 
Eocene until the Pliocene. Affiliation with Aus- 
tralia. 
SOME GEOLOGICAL OBSERVATIONS ON THE CENTRAL PART 
OF THE ROSEBUD INDIAN RESERVATION, 
SOUTH DAKOTA. 
By Albert B. Reagan, Mora, Wash. 
PLATE XII. 
CONTENTS. 
1. Map. 
2. Introduction. 
3. Sections. 
4. Formations in Detail. 
(A) Pierre Shales. 
(B) Oligocene. 
(C) Arikaree. 
(D) Ogallala (?) 
(E) Glacial (?) 
(F) Recent. 
5. Bad Lands. 
6. Buttes. 
7. Rattle Snake Butte. 
S. Minerals. 
9. Soil. 
10. Water (color, taste, alkali). 
11. Sink-holes, ponds and lakes. 
12. Springs. 
13. Streams. 
(A) Why the southern tributaries of White river are building- 
up their channels in their middle courses. 
(B) Change of Drainage Courses. 
(C) Why White river has all of its tributaries on its southern 
side. 
14. Irrigation. 
The region under consideration extends from Valen- 
tine, Nebraska, north to beyond White river, the northern 
boundary of the Rosebud Indian reservation ; and both to 
the east and to the west of the White Thunder day school 
of that reservation a distance of about twenty-five miles. It 
is wholly within the "high plains" region, and is a grazing 
country without trees of any sort except along its streams. 
Geologically the following formations are exposed : the 
