THE HALL OF FOSSIL VERTEBRATES 
which suckle their young, including most four-footed beasts. 
Most of them lived during the Tertiary period, or Age of Mam- 
mals, and are hundreds of thousands of years old, ranging from 
perhaps three million years down; these lived long before man 
had appeared on the earth. A few, including the Mastodon, 
Mammoth, Megatherium, Irish Elk, One-toed Horse and others, 
are of the latest geological age, the Quaternary, or Age of 
Man, and, while tens of thousands of years old, were contem- 
poraries of the earliest human beings. 
Many of the extinct animals are allied to those which are still 
living and are called by the common names of their modern 
relatives. Thus we have extinct Horses, Rhinoceroses, Tapirs, 
Camels etc. Other races have died out completely and are not 
related to any living animals. For these there is no popular 
name, and we have to coin a name from their Latin or Greek 
scientific name, calling them “ Titanotheres,”’ ‘‘ Dinosaurs”’ etc. 
INSTANCES OF EVOLUTION. 
The best example of the evolution of a race of animals is 
shown in the southeastern corner of the hall. Here is exhibited 
the Ancestry of the Horse, the specimens from successive geologi- 
cal strata showing how the Modern Horse has descended from 
diminutive ancestors with four toes on each forefoot and three 
on each hind foot, and with teeth and other parts of the skele- 
ton different from those of their modern representatives. 
Almost equally complete, although less familiar; is the series 
illustrating the Ancestry of the Camel, which may be found on 
the north side of the hall near the east end. These animals, like 
the Horses, evolved from small and primitive ancestors to large 
and highly specialized descendants, and then became extinct in 
their former home, the broad and arid plains of western America, 
before the advent of civilized man, but survived to modern times 
in other parts of the world. Less complete series are the skulls 
and skeletons illustrating the ancestors of Titanotheres and the 
ancestors of Rhinoceroses. These are ranged along the south 
side of the hall beginning at the entrance. 
It 
