FREE-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 J. 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 (Molossus 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 (M. 

 glaucinus), Mr. 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 



