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 {524} 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.

[Ill.u.s.tration]

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. {525} The inner margin of the nostrils projects, a preparation for the tubular nostrils of _Harpyia_. The tail is absent. The premolars are three and the molars two. The pyloric region of the stomach is extended and twisted upon itself. Of this genus there are nearly sixty species, extending from Madagascar to Queensland. Thirty species inhabit the Australian, twenty the Oriental region. Madagascar has seven, and one species just enters the Palaearctic. The occurrence of this genus in India and in Madagascar is one of those facts which favour the view supported, on these and other grounds, by Dr. Dobson and Dr. Blanford that a connexion between India and Madagascar must once have existed; for these slow-flying creatures could hardly be believed capable of traversing vast stretches of ocean by their unaided efforts.[399]

[Ill.u.s.tration]

FIG. 257.--Flying Fox. _Pteropus poliocephalus._ 1/3.

_Pteropus_ is represented in the Ethiopian region by the allied genus _Epomophorus_. Of this there are perhaps a dozen species. The teeth are reduced to two premolars in the upper jaw, {526} three remaining below; while there is but one molar in each upper jaw, and two in each lower. Dr.

Dobson has studied the structure of the remarkable pharyngeal sacs which exist in the neck of the male, and are capable of inflation.

_Pteralopex_ of the Solomon Islands has shorter ears than have many _Pteropus_, otherwise its external characters are the same. As in _Pteropus nicobaricus_, this genus has the orbits shut off by a bony ring, an extremely rare phenomenon in Bats. The canines have two cusps. The characters of the grinding teeth have already been mentioned. It is uncertain whether the only species of this genus, _P. atrata_, is, or is not, a vegetable feeder. _Harpyia_ has shortish ears and extraordinarily prolonged and tubular nostrils. There is a hint of the accessory cusp to the canines mentioned above in _Pteralopex_. The incisors are reduced to one on each upper jaw, and none below. _Cynopterus_ has also often bituberculate canines. It is an Oriental genus with several species.

_Nesonycteris_, with one species from the Solomon Islands, _N. woodfordi_, has the dental formula I 2/1 C 1/1 Pm 3/3 M 2/3. The index finger has no claw; the tail is absent. The premaxillae are separated anteriorly.

_Eonycteris_, with a single cave-dwelling species from Burmah, _E.

spelaea_, has also no claw upon the index; the tooth formula is fuller by reason of the presence of an additional incisor below. The tongue is very long and is armed with papillae. There is a short but distinct tail.

_Notopteris_, from New Guinea and the Fiji Islands, is distinguished from the related genera by its long tail.

The remaining genera of Fruit Bats are _Boneia_, _Harpyionycteris_, _Cephalotes_, _Callinycteris_, and _Macroglossus_, from the Oriental region, and _Scotonycteris_, _Liponyx_, and _Megaloglossus_ from the Ethiopian region; finally, there is the Australian _Melonycteris_.

SUB-ORDER 2. MICROCHIROPTERA.

The members of this sub-order are mostly insectivorous though occasionally "frugivorous or sanguivorous" Bats. The molars are multicuspid with sharp cusps. The palate is not continued back behind the last molar. The second finger has but one phalanx, or {527} none; occasionally there are two. It has no claw. The ear has its two sides separate from their point of origin upon the head. The group is of Old-World distribution.

FAM. 1. RHINOLOPHIDAE.--The Bats of this family possess the leafy outgrowths around the nostrils. The ears are large, but have no tragus. The index finger has no phalanx at all. The premaxillary bones are quite rudimentary, and are suspended from the nasal cartilages. In addition to the pectoral mammae they have two teat-like processes situated abdominally.

The tail is long, and extends to the end of the interfemoral membrane.

The genus _Rhinolophus_ has a large nose leaf, and an ant.i.tragus to the ear. The first toe has two joints, the remaining toes have three joints each. The dent.i.tion is I 1/2 C 1/1 Pm 2/3 M 3/3. There are nearly thirty species of the genus, which are restricted to the Old World. Two species occur in this country, viz. _R. ferrum equinum_, the Great Horse-shoe Bat, and the Lesser Horse-shoe Bat, _R. hipposiderus_. The name is of course derived from the shape of the nose leaf.

The genus _Hipposiderus_ and some allied forms are placed away from _Rhinolophus_ and its immediate allies in a sub-family _Hipposiderinae_.

The type genus _Hipposiderus_, or, as it ought apparently to be called, _Phyllorhina_, is Old World in range, like all the other members of the family.

The nose leaf is complicated, and there are only two phalanges in all the toes; there is no ant.i.tragus to the ear. A curious feature in the osteology of the genus, and indeed of the sub-family, is the fact that the ileo-pectineal process is connected with the ilium by a bony bridge; this arrangement is unique among mammals.

The genus _Anthops_, only known from the Solomon Islands, and represented there by but a single species (_A. ornatus_), has an extraordinarily complicated nose leaf. The tail, like that of the Oriental _Coelops_, likewise represented by a single species (_C. frithii_), is rudimentary.

_Triaenops_, Ethiopian and Malagasy, has, like the Australian _Rhinonycteris_, a well-developed tail. _Triaenops_ has also a highly-complicated nose leaf.

FAM. 2. NYCTERIDAE.--This family is to be distinguished from the Rhinolophidae by the fact that the ear has a small tragus, and by the small and cartilaginous premaxillae. In addition to {528} these two characters it may be added that the nose leaf is well developed, but is not so complicated as in the last family. The type genus _Nycteris_ is Ethiopian and Oriental, nine species being African, and only one, _N. javanica_, being, as the specific name denotes, from the East. _Megaderma_ is to be distinguished by the loss of the upper incisors. There is no tail, and the ears are particularly large. They are carnivorous Bats, and _M. lyra_, called the "Indian Vampire Bat," chiefly affects frogs as an article of diet.

FAM. 3. VESPERTILIONIDAE.--This family has not the nose leaf of other families. The apertures of the nostrils are simple, round, or crescentic apertures. The ear has a tragus, and the tail is not produced to any great degree behind the interfemoral membrane. There are two phalanges to the index digit.

This family in numbers of species is vastly in excess of any other family of Bats. The most recent estimate, that of P. L. and W. L. Sclater, allows 190. But the generic types are by no means so numerous as in the Phyllostomatidae. This is a significant fact when we reflect upon the geographical range of the two families. The Vespertilionidae range over the whole earth, while the Phyllostomatidae are practically limited to the South American continent, only just getting into the Nearctic region. They inhabit, therefore, a more restricted area, and, in consequence of compet.i.tion, have specialised more freely than the widely-spread and therefore not crowded Vespertilionidae.

The genus _Vesperugo_ is by far the largest genus of this family, embracing no less than seventy species. The tail is shorter than the head and body together; the ears are separate, and moderate or short in size; the tragus is generally short and obtuse. The dent.i.tion is I 2, C 1, Pm 2 or 1, M 3.

It is a remarkable fact that this genus, unlike most Bats, produces two young at a time. The genus is universal in range, and one species, the Serotine Bat, known in this country, even ranges from the New World to the Old; but with so small a creature the possibility of accidental transportation by man must not be left out of sight. The British species are--_V. serotinus_, the Serotine already mentioned; _V. discolor_, a single example only of which has occurred, and may have been introduced; _V. noctula_, the habits of which were described by Gilbert White; _V.

leisleri_; and the Pipistrelle, _V. pipistrellus_, which is the best-known member of the genus in this country.

{529}

The genus _Vespertilio_ contains some forty-five species, and is world-wide in range. It has one more premolar in the upper jaw than has _Vesperugo_.

There are no less than six British species, of which _V. murinus_ is the largest species of Bat recorded from this country, but is not quite certainly indigenous.

_Plecotus_ has very long ears. The dent.i.tion is I 2/3 C 1/1 Pm 2/3 M 3/3.

The tragus is very large. There are but two or possibly three species, of which one is North American, and the other is the Long-eared Bat, _P.

auritus_, of this country, but ranging as far as India. The shrill voice, inaudible to some ears, of this Bat has been heard _of_ by everybody.

_Synotus_ includes the British Barbastelle, _S. barbastellus_, as well as an Eastern form. It differs from the last genus princ.i.p.ally by the loss of a lower premolar. The ears, too, are not so large. _Otonycteris_, _Nyctophilus_, and _Antrozous_ are allied genera; the last is Californian, the others Old-World forms.

_Kerivoula_ (or _Cerivoula_) has a long, pointed, narrow tragus. The tail is as long as or longer than the head and body. The dent.i.tion is as in _Vespertilio_; but the upper incisors are parallel instead of divergent as in that genus. The brilliantly-coloured _K. picta_ is, on account of this very fact, the best-known species. The name _Kerivoula_, a corruption of the Cinghalese "Kehel vulha," signifies plantain bat. This Bat has been described as looking, when disturbed in the daytime, more like a huge b.u.t.terfly than a Bat, which is naturally a.s.sociated with sombre hues. Other species occur in the Oriental, Australian, and Ethiopian regions.

_Miniopterus_ has a premolar less in the upper jaw; it has a long tail as in the last genus. One species, _M. scheibersi_, has almost the widest range of any Bat, it being found from South Europe to Africa, Asia, Madagascar, and Australia.

_Natalus_ is an allied form from Tropical America and the West Indies. It is chiefly to be separated from _Kerivoula_ by the short tragus to the ear.

_Thyroptera_ is also South American. It is distinguished by the curious sucker-like discs upon the thumb and foot. These "resemble in miniature the sucking cups of cuttle-fishes." The Madagascar genus, _Myxopoda_, with but one species, has also an adhesive but horse-shoe-shaped pad upon the thumb and foot.

_Scotophilus_ has shortish ears with a tapering tragus. The tail is shorter than the head and body, and is nearly contained within {530} the interfemoral membrane. The dent.i.tion is I 1/3 C 1/1 Pm 1/2 M 3/3, with another upper incisor in the young. It is African, Asiatic, and Australian.

This genus appears to be connected with _Vesperugo_ by Mr. Dobson's proposed genus, or sub-genus as it is generally held to be, _Scotozous_.[400] The genus _Nycticejus_, founded for the inclusion of _Scotozous dormeri_, an Indian species, should, according to Dr. Blanford, replace on grounds of priority the name _Scotophilus_. But as this name (_Nycticejus_) is one introduced by Rafinesque, whose work was so uncertain and untrustworthy, it seems preferable to retain the better-known name of _Scotophilus_, introduced by William Elford Leach.

The genus _Chalinolobus_[401] has short, broad ears with an expanded tragus. A distinct fleshy lobule projects from the lower lip on either side of the mouth. The tail is as long as the head and the body. The dental formula is I 2/3 C 1/1 Pm 2/2 or 1/2 M 3/3. The genus occurs in Africa, Australia, and New Zealand; but the African species, with diminished premolars and pale coloration, have been distinguished as _Glauconycteris_.

FAM. 4. EMBALLONURIDAE.--The Bats belonging to this family have no nose leaf. The tragus is present, but often very small. The ears in this family are often united. There are two phalanges in the middle finger. The tail is partly free, either perforating the interfemoral membrane and appearing upon its upper surface, or prolonged beyond its end. The face is obliquely truncated in front, the nostrils appearing beyond the lower lip.

_Emballonura_ is Australian, Oriental, and Mascarene in range. The ears arise separately, and there is a fairly developed and narrow tragus. The tail perforates the interfemoral membrane. The dental formula is I 2/3 C 1/1 Pm 2/2 M 3/3.

_Rhinopoma_ has the ears united; the incisors are reduced by one on each side of each jaw, and the premolars are similarly reduced, but only in the upper jaw.

_Noctilio_ is an American genus of two or three species, which has one pair of markedly large upper incisors, which completely conceal the outer pair.

On these grounds this Bat was removed from its allies and placed by Linnaeus among the Rodents, an instance of the disadvantage of the artificial scheme of cla.s.sification. The species named _N. leporinus_ has been shown to feed upon fish. {531}

_Furia_, _Amorphochilus_, _Rhynchonycteris_, _Saccopteryx_, _Cormura_, and _Diclidurus_ are other Neotropical genera of the same family.

The genus _Taphozous_[402] has a tail which perforates the interfemoral membrane, appearing on its upper surface; it is capable of being withdrawn.

The premaxillaries are cartilaginous. The dent.i.tion is I 1/2 C 1/1 Pm 2/2 M 3/3. The upper incisors often disappear. Many species of the genus have a gular sac, opening anteriorly between the jaws. This is better developed in the males. The genus ranges from Africa through Asia to New Guinea and Australia. There are some twelve species.

The genus _Molossus_[403] has short legs and well-developed fibulae. The tail is thick and fleshy, and is prolonged far beyond the margin of the interfemoral membrane. The ears are united together above the nose; the tragus is minute. The dent.i.tion is I 1/1 or 1/2 C 1/1 Pm 1/2 or 2/2 M 3/3.

This genus, which is confined to the tropical and subtropical portions of America, has long and narrow wings. The Bats can thus fly rapidly, twist about with ease, and capture strongly-flying insects. There are a large number of species.