THE HALL OF FOSSIL VERTEBRATES 
-Aoyia, science). It tells us of a long period of time before Man 
appeared, probably millions of years, during which Mammals of 
great size and unfamiliar form were the dominant animals—of a 
yet longer era before that, during which huge Reptiles were rulers 
of earth, sea and air—and of other more ancient periods during 
which Amphibians, Fish and Invertebrate animals held sway in 
turn. Vertebrate Paleontology deals only with the higher classes 
of fossil animals, the Vertebrata, or those that have backbones 
(fish, amphibians, reptiles, birds and mammals). For fossils of 
this kind the Bad-Lands of the Western States are the richest 
field, and from there came nearly all the specimens in this hall, 
the greater part of which have been found within the last ten 
years. The hall was opened in 1895.' At the time of writing, 
thirty complete skeletons of extinct animals have been placed 
on exhibition, besides many t mes that number of skulls, limbs 
and other imperfect spec mens. 
To give the visitor a clear idea of these extinct animals, the 
skeletons usually have been removed entirely from the rock in 
which they were found and have been mounted as much as pos- 
sible like skeletons of modern animals; their probable appearance 
and habits are described by the labels and illustrated by water- 
color restorations. The especial interest of the hall lies in the fact 
that it shows so many of the data upon which are based the 
theories of Evolution. The arrangement of the specimens is 
intended to showthe history or evolution of different races of 
animals, chiefly in North America. All the specimens of one race 
or kind of animal have been placed together, the most ancient first, 
the most recent last. All the skeletons in this hall are those of ex- 
tinct animals.? The Mastodon and Great Irish Deer are half-petri- 
fied bone dug out of peat bogs. All the others are petrified (7. e., 
they have been buried so long that they have been converted 
from bone into stone), and have been chiseled out of the solid 
rock. The Megatherium is a plaster cast, taken from bones from 
1 A brief history of the Department will be found in the number of this 
Journat for November—December, rgot. 
2 Four small skeletons, those of the Raccoon, Cat, Opossum and young 
Lamb, have been placed in the cases near their extinct relatives, for comparison. 
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