A MONOGRAPH OF THE BATS OF NORTH AMERICA. 9 



The very exceptional dispositiou iu the bat for the skin from the 

 trunk to extend the entire lengths of the limb, and in the case of the 

 anterior extremity to form enormous webs between the j^roduced dig- 

 its, is associated with an inclination for the ears to become greatly ex- 

 panded and for cutaneous offshoots to appear at tlie muzzle, chin, and 

 the sides of the face. Even the prepuce is disposed to be redundant. 

 Together with this inclination, dermal structures are highly specialized, 

 so that the sebaceous glands, hair follicles, and tactile bodies are well 

 developed. It can be readily surmised that special adaptations for a 

 variety of puri)oses occur in this group of structures, so that secondary 

 sexual characters are found in the gland masses of the skin of the neck, 

 and of the skinfolds, the details in the ears, the pouches of skin, etc., 

 are available for purposes of classification. 



THE EXTERNAL EAR. 



In this connection let us glance at the peculiarities of the external ear. 

 The external ear is markedly modified from the tyi:»e usual in quadrupeds. 

 Its simplest expression is seen iu the Pteropidte and the Rhinolophidae. 

 In these families the widely separated auricular cartilages are closely 

 enwrapped by integument and the tragus is said to be absent. (See be- 

 low.) In such an ear the terms inner and outer borders and tij), exhaust 

 the list which are demanded in their description. In the ears of the 

 remaining families it is far different. The auricle here is expanded to 

 degrees which bring the outer parts to a greater or less degree down- 

 ward and forward on the uj^per parts of the neck and reach the region 

 of the mouth, or even the chin, while the inner border, being guarded 

 by a skin fold which connects the ear to the crown, is disposed to be 

 united with the corresponding part of the ear of the opposite side and 

 extend in varying degrees toward the snout. Skin lappets arise from 

 both inner and outer borders. Those from the inner border from a 

 long appendage which lies in advance as defined in the simple ear and 

 hecomQ^ the internal hem. As a rule it ends as a free lobe inferiorly, 

 which thus becomes the internal basal lobe. The line of the true inter- 

 nal border being always discernible becomes the internal ridge. The 

 external border, which is distinguished from the true external border 

 which now becomes the external ridge is also disposed to form a hem 

 {external hem), which, however, in contrast to the inner is apt to be 

 divided into an upper and a lower part; the upper part forms the first 

 scallop, and the lower the second scallop. The free lower end of the 

 outer border becomes the external basal lobe, which may be separated 

 from the lower scallop by a deep basal notch, or the second scallop may 

 extend across this notch and the external basal lobe and becomes con- 

 tinuous at various distances with the ftice or that over the lower jaw. 

 These parts will not receive distinctive names. In most examples the 

 auricle is also conveniently divided into an anterior and a posterior 

 part, the anterior part is marked, if marked at all, by lines repeating 



