FOSSIL CHIROP TERA 45 
contain only a few fragmentary specimens. They can be traced 
back as far as the Oligocene epoch, without any great change in 
character, but their earlier history is a blank. It appears prob- 
able that they are derived along with the Sabre-Tooth Tigers 
from some undiscovered group of Creodonts more nearly related 
to Paleonictis than to any other known fossil type. 
HYANIDA, oR HyYANAs. 
Fossil Hyznas are common in the cave deposits of the Old World, 
but none have been found in this country. In the older formations 
of Europe there has been found a series of extinct forms which appear 
to connect the Hyznas with primitive Civets (/ctithertum, Palhyena). 
These are not represented in our collections. 
C. PINNIPEDIA, OR SEALS. 
This group of Carnivora is exclusively adapted to marine 
life. They are found fossil in sediments of marine origin, but 
are very rare, and nothing is known of their evolution. They 
are almost unrepresented in our collections. An incomplete 
skull of an extinct species of Walrus found near Atlantic City, 
N. J., shows that the range of this animal formerly extended 
much farther south than now. 
II. CHIROPTERA, OR BATS. 
The Bats are the only mammals capable of true flight, al- 
though there are certain kinds of squirrels, marsupials and the 
so-called “flying lemurs,’ which can extend portions of the skin 
into a sort of parachute to assist them in taking long leaps from 
bough to bough. The wings of Bats are chiefly an extension of 
the skin membrane between the fingers, which are greatly elon- 
gated; those of birds on the contrary are chiefly composed of 
feathers which grow from the whole length of the arm and hand, 
although mainly from the second digit of the hand. 
Fossil remains of Bats are exceedingly rare except in cave deposits, 
and do not teach us much about the evolution of this singular group 
of mammals. They resemble the Insectivora more than any other 
