CHIROPTERA 649 
and with the nasal and labial appendages have been described when 
referring to the nervous system. It remains therefore to consider 
its relative development as part of the organs of flight. 
The extent and shape of the flyingmembranes depend mainly 
on the form of the bones of the anterior extremities, and on the 
presence or absence of the tail. Certain modifications of these 
membranes, however, are met with which do not depend on the 
skeleton, but are related to the habits of the animals, and to the 
manner in which the wing is folded in repose. 
These membranes consist of the ‘“antebrachial membrane,” 
extending from the point of the shoulder along the humerus and more 
or less of the forearm to the base of the pollex, the metacarpal bone 
of which is partially or wholly included in it; 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 the “interfemoral membrane,” 
the most variable of all, which is supported between the extremity 
of the body, the legs, and the calcar (Fig. 297). 
The antebrachial and wing-membranes are most developed in 
those species fitted only for aerial locomotion, which when at 
rest hang with the body enveloped in the wings; but in the family 
Emballonuride, and especially in the subfamily Molossine (the species 
of which are the best fitted of all Bats for terrestrial progression), 
the antebrachial membrane is reduced to the smallest size, and 
is not developed along the forearm, leaving also the pollex quite 
free, and the wing-membrane is very narrow and folded in repose 
completely under the forearm. 
The relative development of the 
interfemoral membrane has been 
referred to above in describing 
the caudal vertebre. Its small 
size in the frugivorous and sangui- « 
vorous species, in which its presence 
would be injurious as impeding 
their motions when searching for Fic. 300.—Frontal sac and nose-leaf in male 
5 and female of Hipposiderus larvatus. (Dobson, 
food as they hang suspended by Proc, Zoot. Soc. 1873.) 
their feet, is easily understood. 
Odoriferous glands and pouches opening on the surface of the outer 
skin are developed in many species, but in most cases more so in 
males than in females, and thus constitute secondary sexual char- 
acters, which will be referred to when treating of the peculiarities 
of certain species. 
All the fossil Chiroptera at present known are true Bats in every 
sense of the word, and therefore throw no light on the origin of the 
order. The earliest representatives of the order occur in beds 
of Upper Eocene (Lower Oligocene) age. 
