of three or four offspring at a birth. Rhogëessa and Tomopeas are allied tropical American types. Murina, with the subgenus Harpiocephalus, has i. 2, p. 2, and includes several small bats distinguished by the prominent tube-like nostrils and hairy interfemoral membrane. M. suilla, from Java, the Malay and neighbouring islands, is a well-known species, and the closely allied M. hilgendorfi is from Japan. The remaining species are from the Himalaya, Tibet and Ceylon; and apparently restricted to the hill-tracts of the countries in which they are found. Next to Vespertilio the genus Myotis (divisible into several subgenera), with i. 2, p. 3, includes the largest number of species, and has rather a wider geographical distribution in both hemispheres, one species being recorded from the Navigator Islands. The species may be recognized by the peculiar character of the pairs of upper incisors on each side, the cusps of which diverge from each other, by the large number of premolars, of which the second upper is always small, and by the oval elongated ear and narrow tragus. The British M. bechsteini and M. nattereri are examples of this group. Cerivoula (Kerivoula), which also has p. 3, is distinguished by the parallel upper incisors and the large second upper premolar. There are numerous African and Indo-Malayan species, of which C. picta, from India and Indo-Malay, is characterized by its brilliant orange fur, and membranes variegated with orange and black. The genus includes delicately formed insectivorous, tropical, forest-haunting bats, whose colouring approximates them to the ripe bananas among which they often pass the daytime.
Another subgroup, Minioptereae, is represented solely by the genus Miniopterus, with i. 2, p. 2. The incisors are separated from one another in front and from the canines; the first phalange of the middle finger is very short, the crown of the head elevated, and the tail long. The genus is represented by some half-dozen Old World species, among which the typical M. schreibersi ranges from Europe, southern Asia, and Africa to Japan and Australasia.
|Fig. 21.—Head of Mastiff-bat (Molossus glaucinus).
|Fig. 22.—Head of Nyctinomops macrotis.|
The last subfamily is that of the Molossinae, included by Dobson in the family Emballonuridae. In this group the premaxillae are in contact or but very slightly separated; the ears are large, with the tragus small; the dental formula is i. 1 (1 or 1), c. 1, p. 1 (2), m. 3; and the fibula is strongly developed. In their blunt muzzles and many other features these bats undoubtedly resemble the Emballonuridae, from the typical members of which they differ by the production of the thick tail far beyond the margin of the interfemoral membrane. They are further characterized by their broad and stout feet, in which the first, and in most cases also the fifth, toe is thicker than the rest, and furnished with long bent hairs; and by the presence of callosities at the base of the thumbs, and a single pair of large upper incisors occupying the centre of the space between the canines. The feet are free from the wing-membrane, which folds up under the fore-arm and legs; the interfemoral membrane is retractile, being movable backwards and forwards along the tail; this power of varying its superficial extent confers on these bats great dexterity in changing the direction of flight. All are able to walk or crawl well, and spend much of their time on trees. The genus Chiromeles, with i. 1, c. 1, p. 1, m. 3, the first hind-toe much larger than and separate from the others, and the widely sundered ears, is represented by C. torquata, a large bat of peculiar aspect, inhabiting the Indo-Malay countries. This species is nearly naked, a collar only of thinly spread hairs half surrounding the neck, and is remarkable for its enormous throat-sac and nursing-pouches. The former consists of a semicircular fold of skin forming a pouch round the neck beneath, concealing the orifices of subcutaneous pectoral glands which discharge an oily fluid of offensive smell. The nursing-pouch is formed on each side by an extension of a fold of skin from the side of the body to the inferior surfaces of the humerus and femur. In the anterior part of this pouch the teat is placed. The typical genus Molossus (fig. 21) includes the mastiff-bats, characterized by the dental formula i. 1 or 1, p. 1 or 2; and by the upper incisors being close together in front. The genus is restricted to the tropical and subtropical regions of the New World. M. obscurus, a small species common in tropical America, inhabits the hollow trunks of palms and other trees and the roofs of houses. The males and females live apart (as is the case in most if not all bats). In West Africa the mastiff-bats are represented by Eomops, with one species; while Nyctinomops includes a number of tropical American species more nearly related to the next genus, in which some of them (fig. 22) were formerly included. The widely spread Nyctinomus, with i. 1 or 1, p. 2 or 1, and the upper incisors separate in front, includes numerous species inhabiting the tropical and subtropical parts of both hemispheres. The lips of the bats of this genus are even more expansible than in Molossus, in many of the species (fig. 22) showing vertical wrinkles. N. toeniotis (or cestonii), one of the largest species, alone extends into Europe, as far north as Switzerland. N. johorensis, from the Malay Peninsula, is remarkable for the extraordinary form of its ears. N. brasiliensis is common in tropical America, and extends as far north as California.
|Fig. 23.—Thumb and leg and foot of New Zealand bat|
(Mystacops tuberculatus), enlarged. (From Dobson.)
Here may be conveniently noticed two very rare and aberrant bats, Myzopoda (or Myxopoda) aurita of Madagascar, and Mystacops (or Mystacina) tuberculatas of New Zealand, the latter of which is believed to be well-nigh, if not entirely, exterminated. Myzopoda and Mystacops.Their systematic position and affinities are somewhat uncertain; but in the opinion of O. Thomas the former should typify a separate family, Myzopodidae, in which the latter may also find a place. From all other bats Myzopoda is distinguished by the presence of a peculiar mushroom-shaped organ at the base of the large ear, and by the union of the tragus with the latter, on the inner base of which it forms a small projection. There are three phalanges in the middle finger; and the whole inferior surface of the thumb supports a large sessile horseshoe-shaped adhesive pad, with the circular margin directed forwards and notched along its edge, while a smaller pad occupies part of the sole of the hind-foot. Mr Thomas regards this bat as related on the one hand to the subfamily Mormopsinae of the Phyllostomatidae, and on the other to the Natalinae among the Vespertilionidae; both these groups being regarded by him as of family rank.
Mystacops resembles Myzopoda in having three phalanges to the middle finger, but differs in that the tail perforates the interfemoral membrane to appear on its upper surface in the manner characteristic of the Emballonuridae. The greater part of the wing-membrane is exceedingly thin, but a narrow portion along the fore-arm, the sides of the body, and the legs, is thick and leathery, and beneath this thickened portion the wings are folded. Other peculiarities of structure are found in the form of the claws of the thumbs and toes, each of which has a small heel projecting from its concave surface near the base, also in the sole of the foot and inferior surface of the leg, as shown in fig. 23. The plantar surface, including the toes, is covered with soft and very lax, deeply wrinkled skin, and each toe is marked by a central longitudinal groove with short grooves at right angles to it. The lax wrinkled integument is continued along the inferior flattened surface of the ankle and leg. These peculiarities appear to be related to climbing habits in the species.
Palaeontology tells us nothing with regard to the origin of the Chiroptera, all the known fossil species, some of which date back to the Oligocene, being more or less closely allied to existing types, and therefore of comparatively little interest. The origin of the order from primitive insectivorous mammals must have taken place at least as early as the Lower Eocene. It is, however, noteworthy that several of the earlier extinct species appear to be related to the Rhinolophidae, which is the most generalized family of the order. Remains of Pteropodidae belonging to existing genera occur in the caves of tropical countries in the eastern hemisphere; and the skeleton of an extinct generic type, Archaeopteropus, has been obtained from the Miocene lignite of Italy, which indicates a form to a certain extent transitional in character between typical fruit-bats and the insectivorous bats. The tail, for instance, which in most modern fruit-bats is rudimentary, with only three or four vertebrae, in the fossil has eight complete vertebrae; while the teeth of the
- Proc. Zool. Soc. (London, 1904), vol. ii.