200 The American Geologist. 
October, 1905 
(2), a complete representation of certain contemporary 
faunas, as was done chiefly by the late professor Edward D. 
Cope (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 cooperation in connec- 
tion with those of other institutions, and large collections 
studied independently in other institutions, notably Prince- 
ton and the Carnegie Museum, have naturally brought into 
a new light some of the important general principles of 
palseozoology. 
T. Progress in the General Principles of Palseozoology. 
Polfpoyeography — The first broader bearing is that of 
past distribution and palseogeography, in which the accuracy 
of our records 1 and thoroughness of our search are working 
a revolution. We are finding the remains of animals which 
have recently arrived from South America, Asia, Europe 2 
and Africa 3 , and it would be impossible to narrow the field 
of American fossil mammalogy even if we desired to do so. 
The broad study of intercontinental evolution and relations 
of the mammals is absolutely essential to a philosophical 
understanding. Those who have followed the rapid recent 
progress of palaeontology ^know that this spirit of uniting 
palaeontology ever more closely with distribution and palaeo- 
geography is that which constantly animates the older as 
well as many of the younger workers in this field. 
Zoological methods — Zoology in the sense of studying 
extinct forms as living organisms is also becoming closer 
day by day, and we are now enjoying the recognition by 
mammalogists (Weber 1 , Beddard") of the absolute necessity 
of coupling the study of ancestral with that of the recent 
forms in all questions both of distribution and of classifica- 
1 Matthew, W. D. A Provisional Classification af the Fresh-cater 
Tertiary of the West. Bull. Amer. Mus. Nat. Hist., vol. xii, 1899, pp. 19-77. 
2 Osborn, H. F. Faunal Relations of Europe and America during the 
Tertiary Period. Ann. N. Y. Acad. Sci., vol. xiii. 1900, pp. 46-56. 
3 Osbokn, II. F. Theory of Successive Invasions of an African Fauna 
into Europe Ann. N. Y. Acad. Sci., vol. xiii, 19C0, pp. 56-5S. 
1 Die Saugethiere 8°, Jena, 3904. 
_' Mammalia. The Cambridge Natural History, S°. 1902. 
