Progress in Mammalian Palaeontology— Osborn. 20; 
Modern Fauna, Higher Placental Radiation. 
Archaic Fauna, Lower Placental Radiation. 
fig. 2. 
Extinction of the lower placenta/ radiation of the Cretaceous, and sudden Introduc- 
tion of the higher placental radiation oj the Tertiary. 
The orders Amblypoda, Condylarthra, Edentata, Creodonta, and earliei 
Primates disappenar in North America. The comparatively modern Ro- 
dentia, Carnivora, Perissodactyla, Artiodactyla, and Proboscidea suddenly 
appear without known ancestors in the Lower Tertiary. No connections 
have thus Ear been traced between this older, archaic fauna and the 
newer fauna. 
II. Progress of Discovery and the New Phylogenetic Prob- 
lems Suggested Thereby. 
My purpose in this section is to give a brief resume of 
the progress during the past ten years, and in our present 
state of knowledge to point out where exploration and re- 
search should principally be directed. 
The general advance has been made in five distinct 
lines, which appear to mark out also the main lines for fu- 
ture research. First, the biological value of more accurate 
geological records (Compare Fig. 1 ). has been recognized; 
as a result the mammalia have been chronologically segre- 
