more strongly developed in males than in females, and may perhaps be partly relegated to the category of secondary sexual characters. But it seems that they have also an important tactile function, and enable the creatures to fly without touching bodies which intrude themselves upon their way. The ears, too, are frequently very large, and it may be supposed that the sense of hearing is correspondingly acute. In the common Long-eared Bat of this country, the ears are not greatly inferior in length to the head and body of the animal combined. The ears are of every variety of shape, and offer characters which are valuable in the systematic arrangement of the members of the order.
Fig. 255.—Skeleton of Flying Fox. Pteropus jubatus. × ⅛. (After de Blainville.)
In the skull of Bats there is very rarely a complete separation between the orbital and temporal fossae; the lachrymal duct is outside the orbit. The tympanics are annular, and in a rudimentary condition. The centra
of the vertebrae tend to become ankylosed in old individuals; the caudals have no processes, but are like those quite at the end of the series in long-tailed animals. The sternum is keeled for the better attachment of the pectoral muscles, the chief muscles of flight. The ribs, which are much flattened, are occasionally ankylosed together by their margins. There is a well-developed clavicle. In the carpus the scaphoid, lunar, and cuneiform are all fused together. In the hind-limb the fibula is rarely fully developed.
The Bats are divisible into two primary groups, which are those of the Megachiroptera and the Microchiroptera.
Sub-Order 1. MEGACHIROPTERA.
Fig. 256.—Skull of Pteropus fuscus. × 3⁄2. (After de Blainville.)
The Pteropodidae are frugivorous Bats, usually of large size. The chief distinguishing feature is the fact that the molars are not tubercular, but marked with a longitudinal furrow, which is, however, concealed in the genus Pteralopex by cusps. The palate is continued back behind the molars. The index finger has three phalanges, and is usually clawed. The ears are oval, and the two edges are in contact at the base of the ear. The tail, if present, has nothing to do with the interfemoral membrane. This group is entirely Old World in range. The genus Pteropus embraces the creatures known as Flying Foxes. They are the largest forms in the sub-order, sometimes having an expanse of wing of 5 feet (this is the case with P. edulis). The muzzle is long, and the face therefore "foxy" in appearance.