
358 THE AMERICAN NATURALIST. [VoL. XXXVI. 
VI. African Radiation of Placentals, chiefly Proboscidea ; Hyracoidea; 
the families Antelopide, Giraffide, Hippopotamidea, etc. 





X ) n 
alll pO | i 
Fic. 3.— Restoration of Antarctica, a hypothetical center of Tertiary adaptive radiation, by ele- 
tion to the 304 ding line, showing old continental lines. (From Osborn 


III. Tug Law of Locat ADAPTIVE RADIATION AS EXHIBITED 
IN RELATED CONTEMPORANEOUS TYPES. 
`- As seen in operation among the ungulates the competition 
and range for food originates the lengthening of limb from 
slow-footed into cursorial types, and the lengthening of teeth 
from short-crowned (brachyodont) into long-crowned (hypso- 
dont) types, and frequently the lengthening of skull from bra- 
Chyceplialic into dolichocephalic types (Osborn, '02a). 
The especial application to paleontology to be noted here is 
: that as these types may have lived together or in proximity 
and resorted to the same water courses for drink, their fossilized 
