Ericulus.-Dentition: i, c, p 3, m; total 36. Vertebræ : C 7, D 17, L 6, S 4, C 9. The single species, E. setosus, is a Hedgehog-like animal, having the whole upper surface and the short tail densely covered with close-set spines. The facial bones are much shorter than in any of the preceding genera, and the first upper incisor is elongated, as in Erinaceus. Judging from the slight development of the cutaneous muscles compared with those of the true Hedgehogs, it is probable that complete involution of the body does not take place.

Subfamily Oryzorictinæ.-Tibia and fibula united; testes near urethra; fur without spines.

Microgale.2-Dentition: i, c, p, m; total 40. This genus

FIG. 295.-Skull of Hemicentetes semispinosus. x 2. (From Mivart, Proc. Zool. Soc. 1871.)

includes M. longicaudata and M. cowani, both of which are small Mouse-like species, the former with a tail double the length of the head and body, and having 43 caudal vertebræ ; teeth like those of Centetes ecaudatus, but, owing to the comparatively much shorter muzzle, not separated by wide spaces, and the last premolar and molar with internal basal processes.

Oryzorictes.3-Represented by two species, O. hova and O. tetradactylus, the latter distinguished by the presence of only four digits in the manus, the three inner having long laterally compressed fossorial claws. The general form of the head and body of the two species known is like that of a Mole. These animals burrow in the rice-fields and do much damage to the crops.

Family CHRYSOCHLORIDE.

Skull conical, not constricted between the orbits, without postorbital process, but with well-developed zygomatic arch and tympanic

1 I. Geoffroy, Ann. Sci. Nat. sér. 2, vol. viii. p. 60 (1837). Journ. Linn. Soc.-Zool. vol. xvi. p. 319 (1882).

Mag. Zool. 1870, p. 50.

2 Thomas,

3 Grandidier, Rev. and

bulla. Upper molars tritubercular, with the crowns very tall. No pubic symphysis; the tibia and fibula united. The eyes are covered by the hairy integument; the ears short and concealed by the fur; the internal generative organs are as in Centetina; the mammæ are thoracic and inguinal and placed in cup-shaped depressions. Habits fossorial. Confined to the southern part of the Ethiopian region, not extending to Madagascar.

This family is closely allied to the Centetida, occupying the same relative position with respect to that family that the Talpida does to the Soricida. Compared with the Talpidae, we find the following differences in the structural adaptation to a fossorial life; the manubrium sterni is not anteriorly elongated, neither are the

FIG. 296.-The Golden Mole (Chrysochloris obtusirostris).

clavicles shortened; but this is compensated for by a deep hollowing out of the antero-lateral walls of the thorax, the ribs in these parts and the sternum being convex inwards. The long clavicles have their distal extremities pushed forward, and the concavities on the sides and inferior surface of the thorax lodge the thick muscular

arms.

3-2

Chrysochloris.-Dentition: i, c, p3, m; total 40 or 36 Vertebræ C 7, D 19, L 3, S 5, C 8. This genus includes some seven or eight South African species, commonly known as Golden Moles (Fig. 296). Those species, in which the molars are reduced to, with a basal talon to the lower ones, and without a prominence in the temporal fossa, have been placed in a separate genus, Chalcochloris, by Professor Mivart. Nearly all the species have the fur of the upper surface of a brilliant metallic lustre, varying from golden bronze to green and violet of different shades. The manus

1 Lacépède, Mém. de l'Institut, vol. iii. p. 493 (1801--read 1799).

has four digits, of which the two outer are small, while the middle ones are large, with immensely powerful claws.

Extinct Types.-The only fossil forms which can be referred to the section of the Insectivora with tritubercular molars are the Leptictide, of the Eocene and Miocene of North America. This family includes the genera Leptictis, Mesodectes, and Ictops, all of which are regarded by Dr. Schlosser as true Insectivora, although they were placed by Professor Cope with the Creodont Carnivora.

Bibliography of Insectivora.-Peters, Reise nach Mossambique-Säugeth. 1852; Id. "Ueber die Classification der Insectivora," Monatsb. Akad. Wissensch. Berlin, 1865, and other papers; Mivart, "On the Osteology of Insectivora," Journ. Anat. and Phys. 1867, 1868, and Proc. Zool. Soc. 1871; Gill, "Synopsis of Insectivorous Mammals," Bull. Geol. and Geog. Survey, U.S.A. Washington, 1875 (includes a general bibliography of the order); Dobson, Monograph of the Insectivora, Systematic and Anatomical, London, 1882-90.

CHAPTER XIII

THE ORDER CHIROPTERA

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 inter-femoral 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 3, c1, p 3, m; 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 mamma, 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