Chapter XIII: The Order Chiroptera (1)

Mammals, having their fore limbs specially modified for flight. The forearm consists of a rudimentary ulna, and a long curved radius. The carpus has six bones supporting a small pollex and four greatly elongated fingers, between which and the sides of the body and the hinder extremities a thin expansion of the integument (the wing-membrane or patagium) is extended. The knee is directed backwards, owing to the rotation of the hind limb outwards by the wing membrane; a peculiar elongated cartilaginous process (the calcar), rarely rudimentary or absent, arising from the inner side of the ankle-joint, is directed inwards, and supports part of the posterior margin of an accessory membrane of flight, extending from the tail or posterior extremity of the body to the hinder limbs (the interfemoral membrane). The penis is pendent; the testes are abdominal or inguinal; the mammary glands thoracic and generally postaxillary; the uterus is simple or with more or less long cornua; the placenta discoidal and deciduate; and the smooth cerebral hemispheres do not extend backwards over the cerebellum. The dental series includes incisors, canines, premolars, and molars and never exceeds _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38.

The animals comprised in this order are at once distinguished by the presence of true wings, and this peculiarity is accompanied by other modifications of bodily structure having special relation to flight. Thus, in contrast to most other mammals, in which the hind limbs greatly preponderate in size over the fore, in the present order the fore limbs immensely exceed the short and weak hinder extremities. The thorax, as giving origin to the great muscles which sustain flight, and containing the proportionately large lungs and heart, is remarkably capacious, and the ribs are flattened and close together; the shoulder-girdle is also greatly developed in comparison with the weak pelvic bones.

Linnæus included the Bats among the Primates, mainly on account of the number of their upper incisors, supposed to be always four, the thoracic position of the mammæ, and the pendent condition of the penis. Many other zoologists, taking into consideration the placental characters and the form of the uterus, have followed him; but it is evident that the situation of the mammæ is related to the necessarily central position of the young during flight, the shortness of the uterine cornua, observable in so many species, to the generally uniparous gestation requiring less room, while the discoidal deciduate placenta is equally present in and characteristic of the Insectivora, many species of which also have the penis pendent. Thus, the reasons for maintaining the Bats in this high position being disposed of, we find in the low organisation of their brain a proof of their inferior status; while furthermore, although they differ widely from all other mammals in external form, it is evident that this is only the result of special adaptation to aerial locomotion; and, taking into account their whole bodily structure, we may accept the view of Professor Huxley that they should merely be regarded as exceedingly modified Insectivora.

So thoroughly, however, has this adaptation for flight been carried out that of all animals the Bats are the least terrestrial, not one of them being equally well fitted for progression on the earth. This is due to the hind as well as the fore limbs being pressed into the service of aerial locomotion. Thus the hind limb is so rotated outwards by the wing-membrane that, contrary to what obtains in all other vertebrates, the knee is directed backwards, and corresponds in position to its serial homologue the elbow. It necessarily follows from this arrangement that when a Bat is on the ground it rests on all fours, having the knees directed upwards; while, in order to bring it into a position for forward progression, the foot rotates forwards and inwards on the ankle. Walking under these circumstances is at best only a kind of shuffle, and that this is fully recognised by the animal is evidenced by its great anxiety to take wing, or, if this be impracticable, to ascend to some point where it can hitch itself up by the claws of the hind legs in its usual position when at rest.

The bones of the skeleton are characterised by their slenderness and the great size of the medullary canals in those of the extremities. The vertebral column is short, and the vertebræ differ very slightly in number and form throughout the species. The general number of the dorso-lumbar vertebræ is 17, of which 12 are dorsal; the cervicals are very broad, but short from before backwards, their breadth being due to the great transverse diameter of the spinal canal rendered necessary by the comparatively large size of the spinal cord, which, after giving off the nerves to the fore limbs and thorax, rapidly diminishes in size, and in the lumbo-sacral region is reduced to a fine thread. Except in the frugivorous _Pteropodidæ_, the vertebræ, from the third cervical backwards, are devoid of neural spines. From the first dorsal to the last lumbar vertebra the spinal column forms a single curve backwards, which is most pronounced in the lumbar region. The centra of the vertebræ are but slightly movable upon each other, and in old individuals appear to become partially ankylosed together. The caudal vertebræ are simple cylindrical bones without processes; their number and length being extremely variable even in closely allied species; and the anterior caudals are generally united to the ischial tuberosities. The relative development of the caudal vertebræ is, indeed, intimately correlated to the habits of the animals; the long tail in the insectivorous forms supporting and controlling the position of the large interfemoral membrane, which appears not only to aid their rapid motions when in pursuit of their prey by acting as a rudder, but also to assist in the capture and retention of the larger insects. In the frugivorous types, on the other hand, this is not required, and the tail is accordingly rudimentary or absent. In all Bats the presternum has a prominent keel for the attachment of the great pectoral muscles. In most species the ribs are much flattened, and in some they are partially ankylosed by their contiguous margins.

The skull is subject to considerable structural variations, even within the limits of a single family. Postorbital processes to the frontals are found only in the _Pteropodidæ_, and some _Nycteridæ_ and _Emballonuridæ_. _Pteropus leucopterus_ and _Pteralopex_ are peculiar in having the orbit completely surrounded by bone. A slender zygomatic arch is present, except in some of the _Phyllostomatidæ_.

The milk-teeth are peculiar in that they are utterly unlike those of the permanent series. They are slender, with sharp recurved cusps; and as a rule are shed at an early period (in the _Rhinolophidæ_ before birth), but may coexist with some of the fully developed permanent teeth. The permanent teeth are subject to great variation of form, although they always have distinct roots. In the Insectivorous types they are acutely cusped, the cusps in those of the upper jaw being arranged in a more or less distinct W; but in the frugivorous forms, like the _Pteropodidæ_ and some of the _Phyllostomatidæ_, the molars are longitudinally grooved or hollowed out.

The pectoral girdle maintains a very constant type. Thus the clavicle is very long, strong, and curved; and the scapula large, oval, triangular, with a long curved coracoid process. The humerus, though long, is scarcely two-thirds the length of the radius. The ulna is rudimentary, its proximal extremity, which articulates with but a small part of the humerus, being ankylosed to the radius; and immediately beyond the joint it is reduced to a slender splint-like bone, extending about as far as the middle of the radius. In all species a detached sesamoid bone exists in the tendon of the triceps muscle. The radius is very long, in some species actually equal to the length of the head and body. The proximal row of the carpus consists of a single bone formed by the united scaphoid, lunar, and cuneiform; which, with the extremity of the radius, forms the radio-carpal joint. In the distal row the trapezium, trapezoid, and magnum vary in size in the different families, the unciform appearing to be the most constant, and the pisiform being generally very small.

The manus is always furnished with five digits. The first, fourth, and fifth digits consist of a metacarpal and two phalanges; but in the second and third digits the number of phalanges is different in certain families. The pollex always terminates in a claw, which—like the proximal phalanx—is best developed in the frugivorous species. In most of the frugivorous _Pteropodidæ_ the second digit is provided with a claw; but in all other Bats this and the remaining digits are unarmed. In the genus _Triænops_ alone a very peculiar short bony process projects from the outer side of the proximal extremity of the terminal phalanx of the fourth digit. The relative development of the digits and their phalanges will be noticed under each family.

As might be expected from the small size of the posterior limbs, the pelvic girdle is relatively weak. The ilia are long and narrow. In the males of most species the pubic bones of opposite sides are very loosely united in front, while in females they are widely separated; and in the family _Rhinolophidæ_ alone do these bones form a symphysis. The ileo-pectineal eminence develops a long pectineal process, which in the subfamily _Hipposiderinæ_ is continued forwards to the anterior extremity of the ilium enclosing a preacetabular foramen unique among mammals. The acetabulum is small and directed outwards and slightly upwards; and with this is related the peculiar position of the hind limb already noticed as one of the chief characteristics of the order. The femur is slender and cylindrical, with a small head and very short neck, and scarcely differs in form throughout the order. The bones of the leg and foot are variable; in the subfamily _Molossinæ_ alone is there a well-developed fibula, while in all other species this bone is either very slender, or cartilaginous and ligamentous in its upper third, or reduced to a small bony process above the heel, as in _Megaderma_, or altogether absent, as in _Nycteris_.

The foot consists of a very short tarsus, and of slender, laterally compressed toes, with much curved claws. The hallux is composed of a metacarpal, a proximal and an ungual phalanx, and is slightly shorter than the other four toes, each of which has an additional phalanx, except in the subfamily _Hipposiderinæ_ and in the anomalous genera _Thyroptera_ and _Myxopoda_, where all the toes have the same number of phalanges as the first digit, and are equal to it in length. In the genus _Chiromeles_ the first digit is thumb-like and separated from the others, and in the typical _Molossinæ_ the first and fifth digits are much thicker than the intermediate toes.

The most noticeable peculiarities in the myology of the order consist in the separated bands or slips into which the platysma is divided, and in the presence of the remarkable muscle termed occipito-pollicalis, which extends from the occipital bone to the base of the terminal phalanx of the pollex.

Although, as already mentioned, the brain presents a low type of organisation, yet probably no animals possess so delicate a sense of touch as the Chiroptera. It is undoubtedly this perceptive power which enabled the individuals deprived of sight, hearing, and smell, in Spallanzani’s well-known experiments, to avoid the numerous threads hung across the rooms in which they were permitted to fly about. In the common Bats the tactile organs evidently exist, not only in the delicate vibrissæ which spring from the sides of the muzzle, but also in the highly sensitive and widely extended integumentary structures entering into the formation of the wing-membranes and ear-conchs; while in many other species, notably in the tropical Rhinolophine and Phyllostomatine Bats, peculiar foliaceous cutaneous expansions surrounding the nasal apertures or extending backwards behind them are added. These structures, collectively known as the “nose-leaf” (whence the term “leaf-nosed Bats”), have been shown by Dr. Dobson to be made up partly of the extended and thickened marginal integument of the nostrils, and partly of the highly differentiated glandular eminences occupying the sides of the muzzle, in which, in all the common Bats, the vibrissæ are implanted.

In all species of leaf-nosed Bats, and especially in the _Rhinolophidæ_, where the nasal appendages reach their highest development, the superior maxillary division of the fifth nerve is of remarkably large calibre. The nasal branch of this nerve, which is given off immediately beyond the infraorbital foramen, is by far the largest portion; the palpebral and labial branches consisting of a few slender nerve-fibres only. This branch passes forwards and upwards on the side of the maxilla, but soon spreads out into numerous filaments extending into the muscles and integument above, and into the base of the nose-leaf. The nerve supply of the nose-leaf is further augmented by the large nasal branch of the ophthalmic division of the fifth nerve. While the many foliations, elevations, and depressions which vary the form of the nose-leaf greatly increase the sensory surface supplied by the fifth nerve, and during rapid flight intensify the vibrations conveyed to it, the great number of sweat and oil glands which enter into its structure perform a function analogous to that of the glands of the auditory canal in relation to the membrana tympani in maintaining its surface in a highly sensitive condition. The nasal appendages of the Chiroptera may thus be regarded as performing the office of an organ of a very exalted sense of touch standing in the same relation to the nasal branches of the fifth nerve as the aural apparatus to the auditory nerve; for, as the latter organ collects and transmits the waves of sound, so the former receives impressions arising from vibrations communicated to the air by approaching objects.

In no order of mammals is the ear-conch so greatly developed or so variable in form. Thus in most of the insectivorous species the ears are longer than the head, while in some, as in the common Long-eared Bat (_Plecotus auritus_), their length nearly equals that of the head and body. The form of the conch is very characteristic of the various families; in most the tragus is remarkably large, in some extending nearly to the outer margin of the conch; and its function appears to be to cause undulations in the waves of sound, and so intensify and prolong them. It is worthy of notice that in the _Rhinolophidæ_, the only family of insectivorous Bats wanting the tragus, the auditory bullæ reach their greatest size, and the highly sensitive nasal appendages their highest development; and that in the typical group of the _Molossinæ_ the ear-conch is divided by a prominent keel; and the antitragus is unusually large in those species in which the tragus is minute (see Fig. 298, _a_). In the frugivorous Bats the form of the ear-conch is very simple, and but slightly variable, throughout the various types.

In all Bats the ears are extremely mobile, each moving independently at the will of the animal. This has been observed even in the frugivorous _Pteropodidæ_, in which the peculiar vibratory movements first noticed in _Artibeus perspicillatus_ may also be seen when the animals are alarmed.

The opening of the mouth is anterior in most species, but in many it is inferior, the extremity of the nose being more or less produced beyond the lower lip,—so much so indeed in the small South-American species _Rhynchonycteris naso_ as to resemble that of the Shrews. The lips exhibit the greatest variety in form, which will be referred to under each family. The absence of a fringe of hairs is characteristic of all fruit-eating Bats, and probably always distinguishes them from the insectivorous species, which they may resemble in the form of their teeth and other respects.

The œsophagus is narrow in all species, and especially so in the sanguivorous Desmodont _Phyllostomatidæ_. The stomach presents two principal types of structure, which correspond respectively to the two great divisions of the order, the Megachiroptera and the Microchiroptera; in the former (with the exception of _Harpyia_) the pyloric extremity is more or less elongated and folded upon itself, in the latter it is simple, as in the Insectivora Vera; a third exceptional type is met with in the Desmodont _Phyllostomatidæ_, where the left or cardiac extremity is greatly elongated, forming a long narrow cæcum-like appendage. The intestine is comparatively short, varying from one and a half to four times the length of the head and body, being longest in the frugivorous and shortest in the insectivorous species. Only in _Rhinopoma microphyllum_ and _Megaderma spasma_ has a very small cæcum been found.

The liver is characterised by the great size of the left lateral lobe, which occasionally equals half the size of the whole organ; the right and left lateral fissures are usually very deep; in the Megachiroptera (_Harpyia_ excepted) the Spigelian lobe is ill-defined or absent, and the caudate is generally very large; but in the Microchiroptera, on the other hand, the Spigelian lobe is very large, while the caudate is small, in most species forming a ridge only. The gall-bladder is generally well developed and attached to the right central lobe, except in the _Rhinolophidæ_, where it is connected with the left central.

In most species the hyoids are simple, consisting of a chain of slender, elongated, cylindrical bones connecting the small basi-hyoid with the cranium, while the pharynx is short, the larynx shallow with feebly developed vocal cords, and guarded by a short, acutely-pointed epiglottis, which in some genera (_Harpyia_, _Vampyrus_) is almost obsolete. In _Epomophorus_, however, we find a remarkable departure from the general type. Thus the pharynx is long and very capacious; the aperture of the larynx is far removed from the fauces, and, opposite to it, opens a canal, leading from the narial chambers, and extending along the back of the pharynx; the laryngeal cavity is spacious and its walls are ossified; the hyoid bone is quite unconnected, except by muscle, with the cranium; the ceratohyals and epihyals are cartilaginous and greatly expanded, entering into the formation of the walls of the pharynx, and in the males of three species at least, supporting the orifices of a large pair of air-sacs communicating with the pharynx (Fig. 299).

In extent, peculiar modifications, and sensitiveness the cutaneous system reaches its highest development in this order. As a sensory organ its chief modifications in connection with the external ear and with the nasal and labial appendages have been described when referring to the nervous system. It remains therefore to consider its relative development as part of the organs of flight.

The extent and shape of the flying-membranes depend mainly on the form of the bones of the anterior extremities, and on the presence or absence of the tail. Certain modifications of these membranes, however, are met with which do not depend on the skeleton, but are related to the habits of the animals, and to the manner in which the wing is folded in repose.

These membranes consist of the “antebrachial membrane,” extending from the point of the shoulder along the humerus and more or less of the forearm to the base of the pollex, the metacarpal bone of which is partially or wholly included in it; the “wing-membrane,” which is spread out between the greatly elongated fingers, and extends along the sides of the body to the posterior extremities, generally reaching to the feet; and the “interfemoral membrane,” the most variable of all, which is supported between the extremity of the body, the legs, and the calcar (Fig. 297).

The antebrachial and wing-membranes are most developed in those species fitted only for aerial locomotion, which when at rest hang with the body enveloped in the wings; but in the family _Emballonuridæ_, and especially in the subfamily _Molossinæ_ (the species of which are the best fitted of all Bats for terrestrial progression), the antebrachial membrane is reduced to the smallest size, and is not developed along the forearm, leaving also the pollex quite free, and the wing-membrane is very narrow and folded in repose completely under the forearm. The relative development of the interfemoral membrane has been referred to above in describing the caudal vertebræ. Its small size in the frugivorous and sanguivorous species, in which its presence would be injurious as impeding their motions when searching for food as they hang suspended by their feet, is easily understood. Odoriferous glands and pouches opening on the surface of the outer skin are developed in many species, but in most cases more so in males than in females, and thus constitute secondary sexual characters, which will be referred to when treating of the peculiarities of certain species.

All the fossil Chiroptera at present known are true Bats in every sense of the word, and therefore throw no light on the origin of the order. The earliest representatives of the order occur in beds of Upper Eocene (Lower Oligocene) age.

The order is divided by Dobson into the suborders Megachiroptera and Microchiroptera.

_Suborder_ MEGACHIROPTERA.

Frugivorous Bats, generally of large size. Crowns of molars smooth, marked with a longitudinal groove (cuspidate in _Pteralopex_); bony palate continued behind the last molar, narrowing slowly backwards; three phalanges in the index finger, the third phalanx generally terminated by a claw; sides of the ear-conch forming a complete ring at the base; tail, when present, inferior to (not contained in) the interfemoral membrane; pyloric extremity of the stomach generally much elongated; the Spigelian lobe of the liver ill-defined or absent, and the caudate well developed.

Limited to the tropical and subtropical parts of the eastern hemisphere.

Mr. O. Thomas[571] considers that the ordinary type of molar dentition found in this suborder is a specialised adaptation from the cuspidate type of the Microchiroptera; the genus _Pteralopex_ retaining the ancestral form of teeth.

_Family_ PTEROPODIDÆ.

Since all the forms are included in this family its characters may be taken to be the same as those of the suborder.

Subfamily =Pteropodinæ=.—Tongue moderate; molars well developed.

_Epomophorus._[572]—Dentition: _i_ ²⁻¹⁄₂, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ¹⁄₂; total 28 or 26. Tail absent or very short, when present free from interfemoral membrane; second digit of manus clawed; premaxillæ united. This genus includes some seven species inhabiting Africa south of the Sahara. The head is large and long, and the lips are expansible, and frequently with peculiar folds. The ears have a white tuft of hair on the margin; and in the males of most species there are large glandular pouches in the skin of the side of the neck near the shoulder, from the mouth of which project long and coarse yellowish hairs, forming tufts on the shoulders, from which the genus takes its name. Another male secondary sexual character consists in the presence of a pair of large air-sacs extending outwards on each side from the pharynx beneath the integument of the neck, in the position shown in Fig. 299. These sacs are evidently capable of being greatly distended at the will of the animal, and their inflation probably occurs under the same circumstances that the wattles of male gallinaceous birds swell up, namely, when engaged in courting the females. Other remarkable conditions in which these Bats appear to differ from all other species occur in the form of the hyoid bones and larynx. These Bats appear to live principally on figs, the juicy contents of which their large lips and capacious mouths enable them to swallow without loss.

_Pteropus._[573]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ²⁄₃; total 34. This genus has more than forty species, and thus includes more than half the members of the family. All are of large size, and the absence of a tail, the long pointed muzzle (Fig. 301), and the woolly fur covering the neck render their recognition easy. They are commonly known as “Flying Foxes,” or Fox-Bats; and one of the species (_P. edulis_) inhabiting Java measures 5 feet across the fully extended wings, and is thus the largest known species of the order. All the species closely resemble one another in dentition, and are mainly distinguished by the form of the ears and the quality of the fur. _P. scapulatus_, from North-East Australia, approaches the species of the second subfamily in the remarkable narrowness of its molars and premolars.

The range of this genus extends from Madagascar and the neighbouring islands through the Seychelles to India, Ceylon, Burma, the Malay Archipelago, Southern Japan, New Guinea, Australia, and Polynesia (except the Sandwich Islands, Ellice’s Group, Gilbert’s Group, Tokelau, and the Low Archipelago). Of the islands inhabited by it some are very small and remote from any continent, such as Savage Island in the South Pacific and Rodriguez in the Indian Ocean. Although two species inhabit the Comoro Islands, which are scarcely 200 miles from the African coast, not a single species is found in Africa; but in India, separated by thousands of miles of almost unbroken ocean, a species exceedingly closely allied to the common Madagascar Fox-Bat is abundant. The Malay Archipelago and Australia are their headquarters; and in some places they occur in countless multitudes. Mr. Macgillivray remarks of _P. conspicillatus_: “On the wooded slope of a hill on Fitzroy Island I one day fell in with this Bat in prodigious numbers, looking while flying in the bright sunshine (so unusual for a nocturnal animal) like a large flock of rooks. On close approach a strong musky odour became apparent, and a loud incessant chattering was heard. Many of the branches were bending under their load of Bats, some in a state of inactivity, suspended by their hind claws, others scrambling along among the boughs, and taking to wing when disturbed.”

_Xantharpyia._[574]—Dentition as in _Pteropus_, but a short tail present, and the fur on the back of the neck similar to that of the body. This genus is represented by some nine species, which have a distribution very similar to that of _Pteropus_, except that they extend into Africa, and are not found in Australia and Polynesia. _X. ægyptiaca_ inhabits the chambers of the Great Pyramid and other deserted buildings in Egypt, and is probably the species so generally figured in Egyptian frescoes. Fig. 302 exhibits an African species of this genus in the attitude assumed by the Fox-Bats when at rest.

_Boneia._[575]—This genus, as represented by _B. bidens_ of Borneo, differs from _Xantharpyia_ in having only a single pair of upper incisors.

_Cynopterus._[576]—Dentition: _i_ ²⁄₂₋₁, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ²⁄₂; total 32 or 30. Muzzle short, grooved like _Pteropus_ in front; tail and fur generally as in _Xantharpyia_, but the former sometimes wholly absent. This genus, with seven species, is almost limited to the Oriental region. _C. marginatus_ is very common in India, and extremely destructive to ripe fruit of every description. Dr. Dobson states that “he gave to a specimen of this Bat obtained at Calcutta a ripe banana, which, with the skin removed, weighed exactly 2 ounces; the animal immediately, as if famished with hunger, fell upon the fruit, seizing it between the thumbs and the index fingers, and took large mouthfuls out of it, opening the mouth to the fullest extent with extreme voracity. In the space of three hours the whole fruit was consumed. Next morning the Bat was killed, and found to weigh one ounce, or half the weight of the food eaten in three hours. Indeed the animal when eating seemed to be a kind of living mill, the food passing from it almost as fast as devoured, and apparently unaltered, eating being, as it were, performed only for the pleasure of eating.”

_Harpyia._[577]—Dentition: _i_ ¹⁄₀, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ²⁄₂; total 24. Premaxillæ well developed and united in front; facial bones much elevated above the margin of the jaw, nostrils tubular (Fig. 303); body and limbs as in _Cynopterus_. Includes two species from the Austro-Malayan sub-region, readily recognised by the peculiar tubular and projecting nostrils, as shown in the accompanying woodcut.

_Cephalotes._[578]—Dentition: _i_ ¹⁄₁, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ²⁄₃; total 28. Premaxillæ separate in front; nostrils simple; muzzle short; index finger without a claw; tail short. Includes one species, having the same distribution as _Harpyia_. The wing-membrane arises from the middle line of the back, to which it is attached by a longitudinal very thin process of the integument; the wings are quite naked, but the back covered by them is clothed with hair.

_Pteralopex._[579]—External characters as in _Pteropus_; ears short and hairy; wings arising from the middle line of the back. Muzzle very short; plane of orbit directed more upwards than in _Pteropus_; orbit surrounded by bone; sagittal crest strongly developed. Teeth cuspidate; upper incisors with broad posterior ledges; upper canine short and thick, with a stout secondary cusp in the middle of the posterior border, and two smaller postero-internal basal cusps; cheek-teeth short and broad, with their anterior and posterior basal ledges so developed and the main cusps so nearly conical as to obliterate the longitudinal grooving of _Pteropus_. Lower incisors very disproportionate, the outer pair being nearly twenty times the bulk of the inner; lower canine stout, with a simple posterior basal ledge. Represented by _P. atrata_ of the Solomon Islands. As already mentioned, Mr. Thomas regards the dentition of this genus as the most generalised type found in the suborder.

Subfamily =Carponycterinæ=.—Facial part of skull much produced; molars narrow, and scarcely raised above the gum; and the tongue exceedingly long, attenuated in the anterior third, and armed with long recurved papillæ near the tip.

_Notopteris._[580]—Dentition: _i_ ²⁄₁, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ²⁄₂; total 28. Index finger without a claw; wings arising from the middle line of the back; tail long; first upper premolar long, with two roots. The single representative of the genus, _N. macdonaldi_, inhabits the Fiji Islands, Aneiteum Island, and New Guinea. It is at once distinguished from all other Bats of this family by the length of its tail, which is nearly as long as the forearm.

_Eonycteris._[581]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ²⁄₃; total 34. First upper premolar small, with a single root. This genus is likewise represented by a single species (_E. spelæa_), from the Farm Caves, Moulmein, Burma, which has somewhat the appearance of _Xantharpyia_; but the absence of a claw to the index finger and the characteristic tongue and teeth at once distinguish it.

_Carponycteris_[582] and _Melonycteris_,[583] each with a single species, are closely allied; the index finger in both has a claw, and the number of the teeth is the same as in _Eonycteris_. _Carponycteris minima_ is the smallest known species of the suborder, being much smaller than the common Noctule Bat of Europe, and its forearm scarcely longer than that of the Long-eared Bat. It is nearly as common in certain parts of India as _Cynopterus marginatus_ (compared with which it is proportionally equally destructive to fruit), and extends eastward through the Malay Archipelago as far as New Ireland, where it is associated with _Melonycteris melanops_, distinguished from it by its larger size and the total absence of the tail.

_Nesonycteris._[584]—Dentition: _i_ ²⁄₁, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ²⁄₃; total 32. Allied to _Melonycteris_, but distinguished by the absence of the inner pair of lower incisors, and of a claw to the index finger. Tail wanting. Represented by _N. woodfordi_, of the Solomon Islands.

_Callinycteris._[585]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 32. Allied to the preceding, but with a short tail; no claw to index. One species from Celebes.

_Trygenycteris._[586]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ²⁄₃; total 34. No external tail; a claw on index. One species from West Africa.

_Suborder_ MICROCHIROPTERA.

Insectivorous (rarely frugivorous or sanguivorous) Bats, of comparatively small size. Crowns of molars acutely cusped, marked by transverse grooves; bony palate narrowing abruptly, not continued backwards laterally behind the last molar; one rudimentary phalanx (rarely two phalanges or none) in the index finger, which is never terminated by a claw; outer and inner sides of ear-conch commencing inferiorly from separate points of origin; tail, when present, contained in the interfemoral membrane, or appearing upon its upper surface; stomach simple (except in the Desmodont _Phyllostomatidæ_); Spigelian lobe of the liver very large, and the caudate generally small. Inhabit the tropical and temperate regions of both hemispheres. The members of this suborder may be divided into two sections.

_Section_ VESPERTILIONINA.

Tail contained within the interfemoral membrane; the middle pair of upper incisors never large, and separated from each other by a more or less wide space. Middle finger with two osseous phalanges only (except in _Myxopoda aurita_, _Thyroptera tricolor_, and _Mystacops tuberculatus_). First phalanx of the middle finger extended (in repose) in a line with the metacarpal bone.

_Family_ RHINOLOPHIDÆ.

In all the species of this family the nasal appendages are highly developed, and surround the sides of the nasal apertures, which are situated in a depression on the upper surface of the muzzle; the ears are large and generally separate, without trace of a tragus; the premaxillæ are rudimentary, suspended from the nasal cartilages, and supporting a pair of very small incisors; the molars have acute W-shaped cusps; the skull is large, and the nasal bones which support the large nasal cutaneous appendages are much expanded vertically and laterally; in the females a pair of teat-like appendages are found in front of the pubis; and the tail is long and produced to the posterior margin of the interfemoral membrane. This family is found in the temperate and tropical parts of the eastern hemisphere.

From whatever point of view the _Rhinolophidæ_ may be considered, they are evidently the most highly organised of insectivorous Bats. In them the osseous and cutaneous systems reach the most elaborate development. Compared with those of the present family the bones of the extremities and the flying-membranes of other Bats appear coarsely formed, and even their teeth seem less perfectly fitted to crush the hard bodies of insects. The very complicated nasal appendages, which evidently act as delicate organs of special perception, here reach their highest development, and the differences in their form afford valuable characters in the discrimination of the species, which resemble one another very closely in dentition and in the colour of the fur.

Subfamily =Rhinolophinæ=.—First toe with two, other toes with three, phalanges each; ilio-pectineal spine not connected by bone with the antero-inferior surface of the ilium.

_Rhinolophus._[587]—Dentition: _i_ ¹⁄₂, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ³⁄₃; total 32. Nose-leaf (Fig. 304) with a central process behind and between the nasal orifices, posterior extremity lanceolate, antitragus large. Includes more than twenty species. _R. luctus_, in which the forearm has a length of 3 inches, is the largest species, inhabiting elevated hill tracts in India and Malayana; _R. hipposiderus_ of Europe, extending into South England and Ireland, forearm 1·5 inches, is one of the smallest; and _R. ferrum-equinum_, with the forearm 2·3 inches in length, represents the average size of the species, which are mainly distinguished from one another by the form of the nose-leaf. The last-named species extends from England to Japan, and southward to the Cape of Good Hope. The genus is represented in the Himalaya by the closely allied _R. tragatus_, distinguished by having three vertical grooves on the lower lip, in place of the single groove found in _R. ferrum-equinum_. _Rhinolophus_ is represented in the Upper Eocene Phosphorites of Central France by _R. antiquus_ and _R. dubius_; the former appears to have the same dental formula as in the existing species, but differs slightly in the structure of some of the lower molars, so that it is separated generically by some writers under the name of _Pseudorhinolophus_. The face is also longer than in existing forms, and there are certain differences in the structure of the skull. _Alastor_, from the same deposits, differs from _Rhinolophus_ by the extreme shortness of the nasal region. _Palæonycteris_, from the Lower Miocene of France, is said to be allied to _Rhinolophus_, but the premolars are ³⁄₃, and the limb bones are stated to resemble those of _Molossus_.

Subfamily =Hipposiderinæ=.—Toes equal, of two phalanges each; ilio-pectineal spine united by a bony isthmus with a process derived from the antero-inferior surface of the ilium.

_Hipposiderus._[588]—Dentition: _i_ ¹⁄₂, _c_ ¹⁄₁, _p_ ²⁻¹⁄₂, _m_ ³⁄₃; total 30 or 28. Tail well developed. This genus, of which more than twenty species have been described, differs from _Rhinolophus_ in the form of the nose-leaf, which is not lanceolate behind and is unprovided with a central process covering the nostrils. The largest species, _H. armiger_, appears to be the most northerly, having been taken at Amoy in China, and in the Himalaya at an elevation of 5,500 feet. Many of the species are provided with a peculiar frontal sac behind the nose-leaf, rudimentary in females (Fig. 305), which the animal can evert at pleasure; the sides of this sac secrete a waxy substance, and its extremity supports a pencil of straight hairs.

_Anthops._[589]—Like _Hipposiderus_, but with the tail rudimentary, consisting merely of three or four vertebræ hidden in the base of the interfemoral membrane. Nose-leaf very complicated, its upright transverse portion emarginate above, and the projections rounded and hollowed behind, and their substance quite thin. Premolars ²⁄₂. Represented by _A. ornatus_ of the Solomon Islands.

Mr. O. Thomas, the describer of this Bat, remarks that it is evidently more nearly allied to the preceding than to the succeeding genera, although it agrees with _Cœlops_ in the rudimentary tail.

_Rhinonycteris_[590] and _Triænops_.[591]—These are two allied genera with well-developed tails; the former being represented by _R. aurantia_ from Australia, and the latter by _T. persicus_ from Persia and Eastern Africa. _Triænops_ (Fig. 306) is characterised by the remarkable form of its nasal appendages and ears, and the presence of a peculiar osseous projection from the proximal extremity of the second phalanx of the fourth finger.

_Cœlops._[592]—This genus is known only by a single species, _C. frithi_, from the Bengal Sunderbans, Java, and Siam (in the roof of the great pagoda at Laos); and is distinguished, not only by the form of its nose-leaf, but also by the great length of the metacarpal of the index finger, as well as by the shortness of the calcar and interfemoral membrane and the rudimental tail.

_Family_ NYCTERIDÆ.

This small family, including only two genera of Bats of peculiar aspect, limited to the tropical and subtropical parts of the eastern hemisphere, is distinguished from the _Rhinolophidæ_ by the presence of a distinct tragus to the ear, and by the premaxillæ being cartilaginous or small and separated from one another in front by a distinct space.

_Megaderma._[593]—Dentition: _i_ ⁰⁄₂, _c_ ¹⁄₁, _p_ ²⁻¹⁄₂, _m_ ³⁄₃; total 28 or 26. This genus, which is represented by five species, is readily recognised by the absence of upper incisors, the cylindrical narrow muzzle surmounted by an erect naked cutaneous nose-leaf, the base of which conceals the nasal orifices, by the immense connate ears with large bifid tragi, and by the great extent of the interfemoral membrane, in the base of which the very short tail is concealed. _M. gigas_ (Fig. 307), from Central Queensland (length of forearm 4·2 inches), is not only the largest species of the genus but also of the suborder. _M. lyra_, common in India (forearm 2·7 inches), has been caught in the act of sucking the blood, while flying, from a small species of _Vesperugo_, which it afterwards devoured, so that it is probable that the Bats of this genus do not confine themselves to insect prey alone, but also feed, when they can, upon the smaller species of Bats and other small mammals.

The Oriental _M. spasma_ and _M. lyra_ differ from the Ethiopian _M. cor_ and _M. frons_ in having two upper premolars instead of one, and also in the shape of the frontals and nasals.

_Nycteris._[594]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ¹⁄₂, _m_ ³⁄₃; total 32. This genus, of which there are seven species, differs so much from _Megaderma_ that it may be considered the type of a separate subfamily. As in that genus, the frontal bones are deeply hollowed out and expanded laterally, the muzzle presents a similar cylindrical form, and the lower jaw also projects, but the single elevated nose-leaf is absent, and instead of it the face is marked by a deep, longitudinal, sharp-edged groove extending from the nostrils (which are on the upper surface of the muzzle, near its extremity) to the low band connecting the bases of the large ears, the sides of this depression being margined as far back as the eyes by small horizontal cutaneous appendages. All the species resemble one another closely, and are mainly distinguished by the form of the tragus and the size and relative position of the second lower premolar. With the exception of _N. javanica_, they are all limited to the Ethiopian region.

_Family_ VESPERTILIONIDÆ.

Nostrils opening by simple crescentic or circular apertures at the extremity of the muzzle, not surrounded by distinct foliaceous cutaneous appendages; premaxillæ small, lateral, and separated by a wide space in front; tragus distinct. In addition to these characters, it may be observed that the skull is of moderate size, the nasal and frontal bones not being much extended laterally or vertically, nor furrowed by deep depressions. The number of incisors varies from ²⁄₃ to ¹⁄₃, rarely (in _Antrozous_ only) ¹⁄₂, premolars ³⁄₃, or ²⁄₂, or ¹⁄₂, rarely (in _Vesperugo noctivagans_ of North America) ²⁄₃; the upper incisors are small, separated by a wide space in the middle line, and placed in pairs or singly near the canine; the molars are well-developed, with acute W-shaped cusps.

This family, which may be regarded as occupying a central position in the suborder, includes the common simple-faced Bats of all countries, of which the well-known Pipistrelle and the Whiskered Bat (_Vespertilio mystacinus_) may be taken as familiar types, and its species number more than 150, or considerably more than one-third the total number of the known species of the entire order. The various genera may be conveniently grouped into the _Plecotine_, _Vespertilionine_, _Miniopterine_, and _Thyropterine_ divisions.

In the _Plecotine_ division, of which the common Long-eared Bat (_Plecotus auritus_) is the type, the crown of the head is but slightly raised above the face-line, the outermost upper incisor is close to the canine, and the nostrils are margined behind by grooves on the upper surface of the muzzle, or by rudimentary nose-leaves; the ears also are generally very large and united.

_Plecotus._[595]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ³⁄₃; total 36. Outer margin of ear-conch ending abruptly near the angle of the mouth, the inner margin with a more or less prominent rounded projection directed inwardly above the base; tragus very large, tapering upwards, with a lobe at the base of its outer margin, rounded, and placed half horizontally. This genus is represented by the European Long-eared Bat (_P. auritus_), and _P. macrotis_, restricted to North America. The latter is distinguished by the great size of the glandular prominences of the sides of the muzzle, which meet in the centre above and behind the nostrils. _P. auritus_ extends over the greater part of the Palæarctic region, occurring in Ireland in the west and the Himalaya in the east.

_Synotus._[596]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 34. This genus is distinguished from the preceding by the loss of one lower premolar and by the outer margin of the ear being carried forwards above the mouth and in front of the eye; it includes the European Barbastelle Bat (_S. barbastellus_) and _S. darjilingensis_ from the Himalaya.

_Otonycteris._[597]—Dentition: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ¹⁄₂, _m_ ³⁄₃; total 30. The reduction in the number of upper incisors readily characterises this genus, which appears to connect the typical representatives of the section, through _Scotophilus_, with the Vespertilionine division. It is represented by a single species, _O. hemprichi_, from North Africa and the Himalaya.

_Nyctophilus._[598]—Dentition: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ¹⁄₂, _m_ ³⁄₃; total 30. This and the following genera are distinguished from all the preceding by the presence of a rudimentary nose-leaf. The present genus contains _N. timoriensis_ of the Australian region, and _N. microtis_ of New Guinea.

_Antrozous._[599]—Dentition: _i_ ¹⁄₂, _c_ ¹⁄₁, _p_ ¹⁄₂, _m_ ³⁄₃; total 28. Readily distinguished from the other members of the whole family by having but two lower incisors, and from the other species of the section by the separate ears. The single species, _A. pallidus_, inhabits California.

The _Vespertilionine_ division includes some nine-tenths of all the representatives of the family. They are distinguished from the preceding section by the simple nostrils, opening by crescentic or circular apertures at the extremity of the muzzle, the generally small size of the ears, and the absence of grooves on the forehead.

_Vesperugo._[600]—Dentition: _i_ ²⁻¹⁄₃, _c_ ¹⁄₁, _p_ ²⁻¹⁄₂₋₃, _m_ ³⁄₃; total 34, 30, or 36. This large genus comprises about one-third of the section, and is divided into groups or subgenera, according to the number of premolars and incisors; the latter varying from ²⁄₃ to ¹⁄₃ in the subgenera _Scotozous_ and _Rhogeëssa_, and the premolars from ²⁄₂ to ¹⁄₂ (in the subgenus _Lasionycteris_ ²⁄₃). The Bats of this genus are generally easily distinguished by their comparatively thickly formed bodies, flat broad heads and obtuse muzzles, short, broad, and triangular obtusely-pointed ears, obtuse and usually slightly incurved tragus, short legs, and by the presence in most species of a well-developed post-calcaral lobule. This lobule (which is supported by a cartilaginous process derived from the calcar) may act as a kind of adhesive disc in securing the animal’s grasp when climbing over smooth surfaces. _Vesperugo_ probably contains the greatest number of individuals among the genera of Chiroptera, and, with the exception of _Vespertilio_, its species have also the widest geographical range, being almost cosmopolitan; and one of the species, the well-known Serotine (_V. [Vesperus] serotinus_) is remarkable as the only species of Bat known to inhabit both the Old and the New World; one (_V. borealis_) has been found close to the limits of the Arctic circle, and another (_V. magellanicus_) inhabits the cold and desolate shores of the Straits of Magellan, being doubtless the Bat referred to by Mr. Darwin in the _Naturalist’s Voyage_. The Common Pipistrelle (_V. pipistrellus_), ranging over the greater part of the Palæarctic region, is the best known species.

_Chalinolobus._[601]—This genus agrees with _Vesperugo_ in the dental formula, but is readily distinguished by the presence of a well-defined lobe projecting near the angle of the mouth from the lower lip, and by the unicuspidate first upper incisor. The species fall into two subgenera—_Chalinolobus_ proper, with _p_ ²⁄₂, represented by _C. morio_ from New Zealand, Tasmania, and Australia, and three other species from Australia; and _Glauconycteris_, with _p_ ¹⁄₂, limited to Southern and Equatorial Africa, and known by _C. argentatus_ and two other species, the Bats of this subgenus being especially remarkable for their peculiarly thin membranes, traversed by very distinct reticulations and parallel lines.

_Scotophilus._[602]—Dentition: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ¹⁄₂, _m_ ³⁄₃; total 30. This genus comprises a comparatively small number of species nearly allied to _Vesperugo_, and some of which approach so closely to the aberrant types of the latter ranged under the subgenus _Scotozous_, as to render the definition of the present genus almost impossible.[603] The species are restricted to the tropical and subtropical regions of the eastern hemisphere, though widely distributed within these limits. The more typical species are distinguished especially by the single pair of unicuspidate upper incisors separated by a wide space and placed close to the canines, by the small transverse first lower premolar squeezed in between the canine and second premolar, and, generally, by their conical nearly naked muzzles and remarkably thick leathery membranes. _S. kuhli_ is probably the commonest species of Bat in India, and appears often on the wing even before the sun has touched the horizon, especially when the white-ants are swarming, feeding eagerly upon them as they rise in the air. _S. gigas_, from Equatorial Africa, with the forearm measuring 3·4 inches, is by far the largest species. _S. albofuscus_, from the Gambia, which is readily distinguished from the other species by its white wings, is an aberrant form, in which the lower premolars are long and not crowded together, and thereby so closely resembles _Vesperugo_ (_Scotozous_) _dormeri_ as to render it almost impossible to distinguish _Scotophilus_ and _Vesperugo_. The figured species is from India.

_Nycticejus._[604]—This genus, with the same dental formula as _Scotophilus_, is distinguished by the first lower premolar not being squeezed in between the adjoining teeth, and by the comparatively much greater size of the last upper molar. It includes only the common North American _N. humeralis_ (_crepuscularis_), a small Bat scarcely larger than the Pipistrelle. It seems, however, as pointed out by Mr. O. Thomas, that the discovery of _Scotophilus albofuscus_ renders the generic distinctness of _Nycticejus_ no longer tenable, and that the species should be known as _Scotophilus humeralis_.

_Atalapha._[605]—Dentition: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ²⁻¹⁄₂, _m_ ³⁄₃; total 32 or 30. The five species of this genus, which are confined to the New World, are generally characterised by the interfemoral membrane being more or less covered with hair (in the two commonest species, _A. noveboracensis_ and _A. cinerea_, wholly covered), and by the peculiar form of the tragus, which is expanded above and abruptly curved inwards. These species have two upper premolars, of which the first is extremely small and quite internal to the tooth-row.

_Harpyiocephalus._[606]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 34. This genus includes some eight species of small Bats distinguished by their prominent tube-like nostrils and hairy interfemoral membrane. _H. suillus_, from Java and neighbouring islands, is the best-known species, and another closely allied (_H. hilgendorfi_)has been described by Professor Peters from Japan. The remaining six species are known only from the Himalaya and Tibet. All appear to be restricted to the hill tracts of the countries in which they are found.

_Vespertilio._[607]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38. Next to _Vesperugo_, this genus includes by far the largest number of species, amounting to over forty; it has, however, rather a wider geographical distribution in both hemispheres, one species at least being recorded from the Navigators’ Islands. The species are easily recognised by the peculiar character of the upper incisors, the crowns of which diverge from each other; by the large number of premolars, of which the second upper one is always very small; and by the oval elongated ear and narrow attenuated tragus. In the British Isles this genus is represented by four species, viz. Bechstein’s Bat (_V. bechsteini_); the Reddish-Gray Bat (_V. nattereri_), of very local occurrence; Daubenton’s Bat (_V. daubentoni_); and the Whiskered Bat (_V. mystacinus_).

_Cerivoula._[608]—This genus, which has the same dental formula as _Vespertilio_, is distinguished by the parallel upper incisors, and the comparatively large size of the second upper premolar. Some ten species have been described from the Ethiopian and Oriental regions, of which _C. picta_, from India and the Indo-Malayan sub-region, is the best-known, being well characterised by its brilliantly coloured orange fur and conspicuously marked membranes, which are variegated with orange and black. This genus includes the most delicately formed and most truly insectivorous, tropical, forest-haunting Bats, which appear to stand as regards the species of _Vespertilio_ in a position similar to that occupied by _Chalinolobus_ with respect to _Vesperugo_.

The _Miniopterine_ division includes only two genera, and is characterised by the great elevation of the crown of the head above the facial line, and also by the upper incisors being separated from the canine and also in the middle line.

_Natalus._[609]—This genus, while having the divisional characters mentioned above, agrees in the dental formula and its general external form with _Cerivoula_, from which it is distinguished by the short triangular tragus. It includes three species, restricted to South and Central America and the West Indies; the head of _N. micropus_ being shown in Fig. 310.

_Miniopterus._[610]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₃, _m_ ³⁄₃; total 36. In addition to the difference in the number of the teeth, this genus is distinguished by the shortness of the first phalanx of the middle finger and the great length of the tail, which is wholly contained within the interfemoral membrane; it includes four species, restricted to the eastern hemisphere. Of these the best-known, _M. schreibersi_, is very widely distributed, being found almost everywhere throughout the tropical and warmer temperate regions of the eastern hemisphere; specimens from Germany, Madagascar, Japan, and Australia differing in no appreciable respect from one another.

The last or _Thyropterine_ division, which likewise comprises only two genera, is characterised by the presence of an additional osseous phalanx in the middle finger and an equal number of phalanges in the toes, and also by peculiar accessory clinging organs attached to the extremities.

_Thyroptera._[611]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38. In the single species _T. tricolor_ of Brazil the clinging organs have the appearance of small, circular, pedunculated, hollow discs (Fig. 311), resembling in miniature the sucking cups of cuttle-fishes, and are attached to the inferior surfaces of the thumbs and soles of the feet. With these the animal is enabled to maintain its hold when creeping over smooth vertical surfaces.

_Myxopoda._[612]—The second genus is likewise represented only by a single species—_M. aurita_ of Madagascar—and is distinguished from the preceding by the characters of the teeth and the form of the ears. The whole inferior surface of the pollex supports a large sessile horse-shoe-shaped adhesive pad, with the circular margin directed forwards and notched along its edge, and a smaller pad occupies part of the sole of the foot.