.

The shape of the skull varies greatly; but post-orbital processes are
developed only in some _Pteropodidae_ and a few _Nycteridae_ and
_Emballonuridae_; in _Pteropus leucopterus_ alone does a process from
the zygomatic arch meet the post-orbital so as to complete the orbital
ring. Zygomatic arches, though slender, are present in all except in
some of the species of _Phyllostomatidae_.

The milk-teeth differ from those of all other mammals in that they are
unlike those of the permanent series. They are slender, with pointed
recurved cusps, and are soon shed, but exist for a short time with the
permanent teeth. In the _Rhinolophidae_ the milk-teeth are absorbed
before birth. The permanent teeth exhibit great variety, sometimes even
in the same family, as in _Phyllostomatidae_, whilst in other families,
as _Rhinolophidae_, the resemblance between the dentition of species
differing in many respects is remarkable. In all they are provided with
well-developed roots, and their crowns are acutely tuberculate, with
more or less well-defined W-shaped cusps, in the insectivorous species,
or variously hollowed out or longitudinally grooved in the frugivorous
kinds.

The shoulder-girdle varies but slightly, the clavicle being long, strong
and curved; and the scapula large, oval and triangular, with a long
curved coracoid process. The humerus, though long, is scarcely
two-thirds the length of the radius; and the rudimentary ulna is welded
with the radius. A sesamoid bone exists in the tendon of the triceps
muscle. The upper row of the carpus consists of the united scaphoid,
lunar and cuneiform bones.

The "hand" has five digits, the first, fourth and fifth of which consist
each of a metacarpal and two phalanges; but in the second and third the
number of phalanges is different in certain families. The first digit
terminates in a claw, most developed in the frugivorous species, in most
of which the second digit is also clawed, although in other bats this
and the remaining digits are unarmed.

In the weak pelvis the ilia are long and narrow, while in most species
the pubes of opposite sides are loosely united in front in males, and
widely separated in females; in the _Rhinolophidae_ alone they form a
symphysis. Only in the _Molossinae_ is there a well-developed fibula; in
the rest this bone is either very slender or cartilaginous and
ligamentous in its upper third, or reduced to a small bony process
above the heel, or absent. T