380 II. F. Osborn — Mammalia in North America. 



Hyopotamidae, in German upon Gelocus, Anthracotherium 

 and Entelodon including the first attempt at an arrangement 

 of a great group of mammals upon the basis of the descent 

 theory. These memoirs swept aside all the dry traditional 

 fossil lore of Europe ; they breathed the new spirit of Darwin, 

 to whom the chief one was dedicated, making principles of 

 descent of more importance than new genera and species. 

 Kowalevsky thus summed up the contemporary paleontology : 



" After the splendid osteological investigations of Cuvier 

 had levealed to science a glimpse of a new mammalian world 

 of wonderful richness, his successors have been bent rather 

 upon multiplying the diversity of this extinct creation, than 

 on diligently studying the organization of the fossil forms that 

 successively turned tip under the zeal of amateurs and collec- 

 tors. . . . With the exception of England (referring to Owen, 

 Huxley, Falconer, and others), where the study of fossil mam- 

 malia was founded on a sound basis, and some glorious excep- 

 tions on the continent (referring to Rtitimeyer, Gaudry, Fraas, 

 Milne-Edwards), we have very few good paleontological me- 

 moirs in which the osteology of extinct mammals has been 

 treated with sufficient detail and discrimination ; and things 

 have come to such a pass, that we know far better the osteology 

 of South American, Australian, and Asiatic genera of fossil 

 mammals than of those found in Europe." 



At the same time, between 1869 and 1873, the pioneers of 

 American paleontology, Leidy, Marsh, and Cope began the 

 exploration of our ancient lake basins rich in life. The first 

 ten vears of their work not only revolutionized our ideas of 

 mammalian descent, but brought together the data for the 

 generalizations of the second decade ; for Marsh's demonstra- 

 tion of the laws of brain evolution in relation to survival ; for 

 Cope's proof of ungulate derivation from types with the 

 simple foot resting upon the sole, and with the conic or buno- 

 dont ancestral molar tooth ; and finally for Cope's demonstra- 

 tion of the tri tubercular molar as the central type in all the 

 mammalia. These four generalizations furnished a new work- 

 ing basis for morphology and phylogeny. 



In these twenty years, thanks to energetic field work, we 

 have accumulated vast materials for the history of the rise of 

 the mammalia, enough for ten students where there is one, 

 and the question arises : how shall we take best advantage of 

 it, what methods shall we adopt? In this address, besides 

 bringing before you the more recent achievements of explora- 

 tion and research, I will try to illustrate the advances already 

 made in lines of thought, observation and system in paleon- 

 tology and indicate other advances which seem to me still 

 desirable. In the problem of how to think and work most 



