FPREE-TAILED GROUP. 295 
specimens has been to confirm these inductions, made upon the evidence of 
structural peculiarities. 
The mastiff-bats are an American group, found in the tropical and subtropical 
regions of both divisions of the Western Hemisphere. With the exception of two 
species, in which the number of the lower incisor teeth is reduced to a single pair, 
they have either 26 or 28 teeth, of which } on either side are incisors, while the 
cheek-teeth number either ¢ or ?. The upper incisors are placed close together in 
the middle line; and the large ears, which have a small tragus (occasionally absent) 
are united by their inner margins. In common with two nearly allied genera of 
bats, they have very capacious lips, which in most of the species are thrown into a 
number of wrinkles or puckers; and they are further characterised by their long 
and slender wings. ‘The great length and narrowness of the wings indicates, as Dr. 
Dobson observes, rapid flight ; and since they also possess the power of varying the 
length of the membrane between the legs by a “reefing” process, they must have 
great dexterity in suddenly changing their direction, as when they are compelled to 
double in pursuing swiftly flying insects; and, again, their expansive and capacious 
lips aid the teeth in seizing and retaining the round and solidly armoured bodies 
of the larger beetles; so that it would seem that they are better adapted than any 
other members of the order for capturing insects of very swift flight. 
Of the red mastiff-bat (M/olossus rufus) an account is given by Mr. P. H. Gosse, 
from which it appears that this bat inhabits the roofs of houses and the hollow trunks 
of palm trees, where colonies of large size may sometimes be found. It is more 
active when on the ground than any other species; and, indeed, on such occasions 
its motions are so rapid that some dexterity is required to ensure its capture. In 
the act of running it rests on its wrists, with the fore-part of the body considerably 
raised. In the hollow stem of a palm tree, examined by another observer, it was 
found that while in one place the males of this species were collected together to 
a number approaching two hundred, in another spot the assemblage consisted 
almost entirely of females, with only a solitary male among them here and there. 
This distinction of the resting-places of the two sexes has also been noticed in 
certain other bats. 
In describing the habits of another species, the chestnut mastiff-bat (I. 
glaucinus), Myr. Gosse writes that “soon after sunset we hear the scrambling of 
little claws along the plaster (in the loft above) gradually tending towards the 
point where the hole under the eaves is situated . . . I judge that they crawl along 
one after another in a straight line to the outlet, in parties. The family assured 
me that after the mastiff-bats had emerged a few hours, they invariably returned 
into the hole again; and they several times directed my attention to them when 
returning. They return between eight and nine o'clock, and issue forth again 
before the morning twilight. When handled, its impatience of confinement is 
manifested by a continuous screeching, not very loud, but exceedingly harsh and 
shrill. The ears are commonly so pendent as completely to cover the eyes; but 
they are occasionally retracted so as to expose the eyes, especially if the face be 
touched.” 
In certain parts of the Amazon Valley the mastiff-bats, together with some 
species belonging to the under-mentioned nose-leafed family, are so numerous as to 
