MAMMALS OF MINNESOTA. 19 



CHAPTER IT. 



ORDER CHIROPTERA 



THE BATS. 



This remarkable group of animals is at once the least under- 

 stood and most interesting of the mammalia. The order is a 

 large one, including over four hundred species which are very 

 artificially arranged in from fifty to sixty genera. North 

 America is quite poor in species as compared with the tropical 

 regions of both hemispheres. The number of species in the 

 United States does not exceed twenty, only five of which are 

 as yet known to enter the limits of our state. 



The bats are very abruptly separated from all other animals 

 whatever, and even the paleontological records reveal no inti- 

 mate relationship with other mammals. The oldest known 

 bats, remains of which have been found in the rocks, are as 

 distinctly bat-like and as little like other mammals as those 

 which now flit about upon moon-lit evenings. 



Bats are primarily distinguished from all other mammals by 

 the possession of true wings. There are, indeed, flying squir- 

 rels, flying marsupials and flying lemurs, but in none of these 

 cases is flight occasioned by true wings formed by the modifica- 

 tion of the anterior extremities. Sharing this peculiarity as 

 they do with birds alone among vertebrates, there are vastly 

 fewer points of similarity than of difference between the two 

 groups. The wing of a bird is produced, it is true, from the 

 hand and arm, but in a far less perfect manner, or anatomically 

 considered, at a great sacrifice of the pentadactyl plan on 

 which the hands of most vertebrates are framed. That the less 

 perfect instrument is able to effect more vigorous and longer 

 sustained flight in many cases is due to other reasons, such as 

 the superior lightness of the frame of birds. There are but 

 two evident fingers in birds and only three are represented by 

 bones. Bats commonly possess five more or less perfect digits, 

 four of which constitute the ribs for the support of the delicate 

 and sensitive web which is the chief instrument of support 



