INTEODtJOTION. XXVll 



sence or absence of the tail. Certain modifications of these mem- 

 branes, however, are met with which evidently do not depend upon 

 the skeleton, but are related to the habits of the animals, and to the 

 manner in which the wing is folded in repose. 



The volar membranes consist of : — (1) the " antebrachial mem- 

 brane," which extends from the point of the shoulder along the 

 humerus and more or less of the forearm to the base of the thumb, 

 the metacarpal bone of which is partially or wholly included in it ; 

 (2) the " wing-membrane," which is spread out between the greatly 

 elongated fingers, and extends along the sides of the body to the 

 posterior extremities, generally reaching to the feet ; and (3) the 

 " interfemoral membrane," the most variable of all, which is sup- 

 ported between the extremity of the body, the legs, and the calcanea. 

 {Vide Plates I., VI., XIII.) 



The antebrachial and wing-membranes reach their highest deve- 

 lopment ill those species which are fitted only for aerial locomotion, 

 and which when at rest hang head downwards suspended by the 

 claws of the hind feet, with the body enveloped in the wings. We 

 find these membranes therefore well developed in the Pteropodidce, 

 in Nycteridce especially, in most species of the Vespertilionidce, and 

 in nearly aU the Phyllostomidce except the group Desmodontes. In 

 Emhallonuridce, especially in the subfamily Molossince (the species 

 of which are, of all Bats, the most fitted for terrestrial progression), 

 the antebrachial membrane is reduced to the smallest size, and is 

 not developed along the forearm, leaving also the thumb quite free, 

 and the wing-membrane is very narrow and folded in repose com- 

 pletely under the forearm (see pp. 403, 444). 



Owing to the peculiar manner in which the wing is folded in 

 nearly all the species of Emhallonuridce, the margin of the membrane 

 between the fourth and fifth fingers is deejdy concave, and does not 

 extend to the end of the terminal phalanx of the fifth finger. 



In all species of Megachiroptera the wing-membrane extends to 

 the backs of the feet, in some species to the backs of the first pha- 

 langes of the toes ; whereas in Microchiroptera (with the exception 

 of the genera Vampyrus and Lophostoma) it is attached to the sides 

 of the legs or feet, rarely to the bases of the calcanea. In most 

 species this membrane has its origin from the sides of the body more 

 or less removed from the spine ; but in Notopteiis and Cephalotes, 

 and in the single species Chilonycteris (Pteronotus) davyi, it arises 

 from the centre line of the back, to which it is connected by a short 

 and very slender longitudinal membranous process ; and while the 



