FOSS/L CHIROPTERA 27 



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 earHer 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 Palaonictis than to any other known fossil type. 



Hy.-enid.-e, or HY.4i:xAS. 



Fossil Hyaenas 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 Hyaenas with primitive Civets {I ctitherhim , Palhyccna). 

 These are not represented in our collections. 



C. PINNIPEDIA, OR SEALS. 



This group of Camivora 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 



