H. F. OSBORN — MAMMALIAN PALÆONTOLOGY 87 
but also more thorough as well as guided by the constantly broadening 
aspects of the science. 
The initial plan ofthe palæozoological survey undertaken by the Ame- 
rican Museum was threefold ; it was so far as possible to secure not only 
(1)a complete representation of certain families of mammals,as was done 
for monographie purposes by Marsa (i.e. Dinocerata, Brontotheriidæ) (2), 
a complete representation of certain contemporary faunas, as was done 
chiefly by the late Professor Edward D. Core (e. g. the Puerco and John 
Day faunas), but in addition (3) to secure complete phyletic series of various 
families of mammals in successive geological horizons from their intro- 
duction to their extinction (compare Fig. 2). In each of these features 
of our plan we have been rewarded with a success far beyond our most 
sanguine expectations. Our large collections studied by friendly coope- 
ration in connection with those of other institutions, and large collec- 
tions studied independently in other institutions, notably Princeton and 
the Carnegie Museum, have naturally brought into a new light some of 
the important general principles of palæozoology. 
I. PROGRESS IN THE GENERAL PRINCIPLES OF PALÆOZOOLOGY 
Palæogeography. — The first broader bearing is that of past distribu- 
tion and palæogeography, in which the accuracy of our records! and 
thoroughness of our search is working a revolution. We are finding the 
remains of animals which have recently arrived from South America, 
Asia, Europe? and Africa, and it would be impossible to narrow the 
field of American fossil mammalogy even if we desired to do so. The 
broad study of the intercontinental evolution and relations of the mam- 
mals is absolutely essential to a philosophical understanding. Those who 
have followed the rapid recent progress of palæontology know that this 
spirit of uniting palæontology ever more closely with distribution and 
History was founded with the present writer as Curator in 1891. Associated with 
him at various times were the following zoologists and palæontologists: Messrs. 
WorTMAN, MATTHEW, EARLE, GipLey, and Browx. Fossil mammals brought from the 
West, secured by exchange, and by purchase, including the entire collection of the 
late Professor Edward D. Core, now number 9873. The CoPe Reptilian and Amphi- 
bian Collection is also in the American Museum. 
1 MarrHew, W. D. À Provisional Classification of the Freshwater Tertiary of 
the West. Bull. Amer. Mus. Nat. Hist. Vol. XII, 1899, pp. 19-77. 
2? OsBorx, H. F. Faunal Relations of Europe and America during the Tertiary 
Period. Ann. N. Y. Acad. Sci. Vol. XIII, 1900, pp. 46-56. 
$ Ossor, H. F., Theory of Successive Invasions of an African Fauna into 
Europe. Ann. N. Y. Acad. Sci. Vol. XIII, 1900, pp. 56-58. 
