ered surfaces of rocks and bark. As evening approaches it appears
on the wing, flying close to the water. _Saccopteryx_ has _i._ 1/3 and
the antibrachial membrane with a pouch opening on its upper surface;
it contains several species from Central and South America. This sac
is developed only in the male and in the female is rudimentary. In
adult males a valvular longitudinal opening occupies the upper surface
of the membrane leading into a small pouch, the interior of which is
lined with a glandular membrane secreting an unctuous reddish
substance with a strong ammoniacal odour. Allied genera are the
tropical American _Peropteryx_ and the Brazilian _Cormura_. The
various species of tomb-bats (_Taphozous_) inhabit the tropical and
subtropical parts of all the eastern hemisphere except Polynesia, and
are distinguished by the cartilaginous premaxillaries, the deciduous
pair of upper incisors, and the presence of only two pairs of lower
incisors. Most of the species have a glandular sac (fig. 15) between
the angles of the lower jaw, more developed in males than in females,
in some species absent in the latter. An open throat-sac is wanting in
_T. melanopogon_, but about its position are the openings of small
pores, the secretion from which probably causes the hairs to grow
long, forming the black beard found in many males. The three tropical
American white bats, _Diclidurus_, with _i._ 1/3, _c._ 1/1, _p._ 3/2,
_m._ 3/3, resemble _Taphozous_ in the form of the head and ears, but,
besides other characters, differ from all other bats in possessing a
pouch, opening off the centre of the interior surface of the
interfemoral membrane; the extremity of the tail enters this, and
perforates its base.

[Illustration: FIG. 15.--Heads of Tomb-Bat (_Taphozous longimanus_),
showing relative development of throat-sacs in male and female. From
Dobson.]

The second subfamily of the _Emballonuridae_, _Rhinopomatinae_, is
represented only by the genus _Rhinopoma_, with several species
ranging from Egypt through Arabia to India, Burma and Sumatra. The
premaxillae (fig. 16) are complete; the index finger has two
phalanges; the tail is very long and mouselike; and the dental formula
_i._ 1/2, _c._ 1/1, _p._ 1/2, _m._ 2/3. Dr G.E. Dobson has remarked
that these mouse-tailed bats might be elevated to the rank of a
family, for it is difficult to determine their affinities, a k