This order in the system of Linnæus includes Man, the Monkeys, the Lemurs, and the Bats. By common consent of all zoologists the last-named animals have been removed into a distinct order; but with regard to the association of the others there has been, and still is, much difference of opinion.

That all the Monkeys, from the highest Anthropoid Apes to the lowest Marmosets, form a natural and tolerably homogeneous group seems never to have been questioned; but whether the Lemurs on the one hand and Man on the other should be united with them in the same order are points of controversy. If, in accordance with the traditional views of zoologists, the former are still considered to be members of this order, they must form a suborder apart from all the others, with which they have really very little in common except the opposable hallux of the hind foot, a character also met with in the Opossums, and which is therefore of very secondary importance.[640]

Using the term Primates in this wider sense it is not easy to give any precise definition of the order. The dentition is diphyodont and heterodont; the number of incisors being very generally ²⁄₂, and that of the molars, with the exception of the Hapalidæ, being ³⁄₃. The cheek-teeth are adapted for grinding, the molars being more complex than the premolars, and usually having four main tubercles, which may be either subconical or more or less compressed. The orbit is invariably surrounded by a ring of bone; the clavicles are well developed; and the radius and ulna are never united. The scaphoid and lunar of the carpus, and commonly also the centrale, remain distinct from one another. There are usually five digits furnished with well-developed nails in both the manus and the pes; but the pollex may be rudimentary or wanting. The hallux, except in Man, is opposable to the other digits, and has a flat nail (absent in Simia); and the pollex, when present, is usually also more or less opposable. The terminal phalanges of the digits are flattened (except in the second digit of the pes of the Lemuroidea), and not cleft at their extremities. The fingers and toes generally do not taper towards their extremities, but (except in Chiromys) are dilated, flattened, and rounded at their tips. The humerus has no entepicondylar foramen, nor the femur a third trochanter. In the alimentary canal (Fig. 324) the stomach is generally simple, although sacculated in the subfamily Semnopithecinæ of the Cercopithecidæ; and there is always a cæcum, which is generally of large size. The placenta may be either non-deciduous, or discoidal and deciduous. There are always two mammæ in the pectoral region, except in Chiromys; and the testes descend into a scrotum.

The Lemuroidea are decidedly low in the scale of organisation, their placentation being of a lower type than that of the Insectivora; and all the Primates retain generalised features in their pentadactylate limbs and more or less bunodont cheek-teeth. In respect to cerebral characters and other features the higher representatives of the order have, however, acquired a specialisation clearly indicating their right to occupy the highest position in the animal kingdom. So far as the available material admits of forming an opinion, fossil forms appear to indicate an intimate connection between the Lemuroidea and Insectivora, so that in some cases it is almost impossible to determine whether an extinct type should be referred to the former or to the latter group. It is noteworthy that while in all existing Primates the upper molars are of a quadrituberculate type, in the extinct Lemuroid genus Anaptomorphus they are trituberculate.

Suborder Lemuroidea.

The Latin term Lemur was applied by Linnæus to the typical representatives of the present group of Primates, having been suggested by the nocturnal habits and strange ghost-like appearance of some of its members. As these animals had previously no vernacular appellation in English, this name has been generally adopted, and is now completely anglicised, making “Lemurs” in the plural. The French call them Makis, and the Germans Halbaffen, in allusion to their forming a transition from monkeys to ordinary quadrupeds. For the same reason they are called Prosimiæ by some systematic writers. When the name was bestowed by Linnæus only five species were known, of which one, L. volans, Linn. (Galeopithecus volans of modern writers), is now removed by common consent from the group. Notwithstanding the discovery of many new and curious forms, the Lemurs remain a very natural and circumscribed division of the animal kingdom, though no longer considered a single genus, but divided up into many genera and even families.

The existing species are not numerous, and do not diverge widely in their organisation or habits, being all of small or moderate size, all adapted to an arboreal life, climbing with ease, and, as they find their living, which consists of fruits, leaves, birds’ eggs, small birds, reptiles, and insects, among the branches of the trees, they rarely have occasion to descend to the ground. None are aquatic, and none burrow in the earth. Many of the species, although by no means all, are nocturnal in their habits, spending the day in sleeping in holes, or rolled up in a ball, perched on a horizontal branch, or in the fork of a tree, and seeking their food by night. Their geographical distribution is very peculiar; by far the larger proportion of species, including all those to which the term “Lemur” is now especially restricted, being exclusively inhabitants of Madagascar, where they are so abundant and widely distributed that it is said by M. Grandidier, who has contributed more than any other traveller to enrich our knowledge of the structure and manners of these animals, that there is not a little wood in the whole island in which some of them cannot be found. From Madagascar as a centre a few species less typical in character extend through the African continent westward as far as Senegambia, and others are found in the Oriental region as far east as the Philippine Islands and Celebes.

The following are the essential characters by which the suborder as a whole is distinguished from the Anthropoidea. Skull with the orbit opening freely into the temporal fossa beneath the postorbital bar (except in Tarsius); and the lachrymal foramen situated externally to the margin of the orbit (Fig. 327). The pollex and hallux are always well developed, the latter being especially large; the second or index digit of the manus may be rudimentary; while in the pes the second digit invariably terminates in a long pointed claw. The cerebral hemispheres do not completely overlap the cerebellum, and are but slightly convoluted. The uterus is bicornuate. The placenta is non-deciduate, and either diffused or bell shaped—the whole of the chorion except the cephalic pole being covered with villi; and the allantois is of very great size. There may be abdominal mammæ. Except in Chiromys, the first pair of upper incisors are separated in the middle line. In marked contrast to the Anthropoidea, the middle or transverse portion of the colon is almost always folded or convoluted on itself. (See Fig. 324.)

In subdividing the group for the purpose of a more detailed description of the different animals of which it is composed it must first be noted that there are two very aberrant forms, each represented by a single species—the little Tarsius of the Indian archipelago, and the singular Chiromys or Aye-aye, which, though an inhabitant of Madagascar, the headquarters of the suborder, and living in the same forests and under the same external conditions as the most typical Lemurs, exhibits a most remarkable specialisation in the structure of its limbs and teeth, the latter being modified so as to resemble, at least superficially, those of the Rodents, in which order it was once placed. The differences between these two forms and the remaining Lemurs are so great that the whole suborder naturally divides itself into three families, the first of which may be again divided into four subfamilies.

Family Lemuridæ.

Upper incisors two on each side, small and separated by an interval in the middle line. Upper canine large, conical, compressed, and pointed. Premolars two or three, molars three on each side above and below, with numerous more or less pointed cusps. In the front of the lower jaw are on each side two or three closely approximated, long, slender teeth lying almost horizontally and projecting forwards. These are generally considered to represent the incisors and canine, but there is some doubt about their homologies, and they may be all considered as incisors, the canine being absent. The first lower premolar larger than those behind it, and shaped like a canine, of which it performs the function (Fig. 327). The orbit and temporal fossa widely continuous beneath the bar of bone (formed by the frontal and jugal) constituting the posterior boundary of the former cavity. The fibula well developed and distinct from the tibia. All the digits of both feet (except the second of the hind foot) with flat nails, and corresponding form of ungual phalanges.

Subfamily Indrisinæ.—The dentition of the adult consists of thirty teeth, usually expressed by the formula i ²⁄₁, c ¹⁄₁, p ²⁄₂, m ³⁄₃; but, as indicated above, they may be i ²⁄₂, c ¹⁄₀, p ²⁄₂, m ³⁄₃. In the milk-dentition there are twenty-two teeth, the true molars of course not being represented, but there are two additional teeth in the fore part of the lower jaw which have no successors in the permanent series. Hind limbs greatly developed, but the tarsus normal. Hallux of large size, and very opposable. The other toes united at their base by a fold of skin, which extends as far as the end of the first phalanx. Mammæ two, pectoral. Cæcum very large, and colon extremely long and spirally coiled.

The animals of this group are, as their organisation indicates, essentially arboreal, and feed exclusively on fruit, leaves, buds, and flowers. They are restricted geographically to the island of Madagascar. Among them are the largest members of the suborder. A detailed and beautifully illustrated account of their characters, external and internal, and distribution and habits, is given in the Histoire Naturelle de Madagascar, by A. Grandidier and Alphonse Milne-Edwards (1875). The species are not numerous and are distributed into three genera.

Indris.[641]—Upper incisors subequal in size. Upper canine larger than the first premolar. Muzzle moderately long. Ears exserted. Carpus without an os centrale. Tail rudimentary. Vertebræ: C 7, D 12, L 9, S 4, C 9.

The only well-established species is the Indris (I. brevicaudata, Fig. 325), discovered by Sonnerat in 1780. It is the largest of the Lemurs, the length of the head and body being about 2 feet, and the tail 2 inches. It is very variable in colour, for although usually nearly black, marked with whitish spots principally in the lumbar region and forearm, individuals have been found quite white. It inhabits exclusively the forests of a part of the east coast of Madagascar, living in small troops of four or five in number, and resembling in most of its habits the animals of the next genus.

Propithecus.[642]—Second upper incisor much smaller than the first. Upper canine larger than the first premolar. Muzzle rather short. Ears short, concealed by the fur. An os centrale in the carpus. Tail long. Vertebræ: C 7, D 12, L 8, S 3, C 28.

The species are all subject to great variations in colour, which has led to much difficulty in discriminating them, and to much confusion of synonymy. Grandidier and Milne-Edwards recognise three as certainly distinct—P. diadema, P. verreauxii, and P. coronatus (Fig. 326). Some of these are to be found in almost every part of the island of Madagascar, living in the woods in small bands of six or eight together, and feeding exclusively on buds, flowers, and berries. Their powerful hind limbs enable them to leap from tree to tree, often to a distance of 10 yards, without any apparent effort, and thus seeming to fly through the air. When obliged to descend to the ground to pass from one clump of trees to another they do not run on all fours, but stand erect, and throwing their arms above their heads progress by a series of short jumps, producing an effect which is described by travellers who have seen them thus in their native haunts as exceedingly ludicrous. They are not nocturnal, but most active in the morning and evening, remaining seated or coiled up among the branches during the heat of the day. They are naturally of a quiet and gentle disposition, and do not show much intelligence. All the species are also less vociferous than the true Lemurs, only when alarmed or angered making a noise which has been compared to the clucking of a fowl. Like the rest of the subfamily they never have more than a single young one at a time.

Avahis.[643]—Second upper incisor larger than the first. Upper canine scarcely larger than the first premolar. Muzzle very short. Ears very small and hidden in the fur, which is very soft and woolly. Carpus without an os centrale. Tail long. Vertebræ: C 7, D 11, L 9, S 3, C 23.

One species, A. laniger, the Woolly Lemur, or Avahis, considerably smaller than any of the last genus. It differs from them in its habits, being quite nocturnal, and not associating in small troops, but being always met with either alone or in pairs. It is very slow in its movements, and rarely descends to the ground, but when it does it walks upright like the other Indrisinæ. It is found throughout the forests which clothe the mountains on the east coast of Madagascar, and also in a limited district on the north-west coast, the specimens from the latter locality being of smaller size and rather different in colour.

Subfamily Lemurinæ.—The dentition in the adult consists of thirty-six teeth, which, as usually enumerated, are i ²⁄₂, c ¹⁄₁, p ³⁄₃, m ³⁄₃. In the fore part of the lower jaw are on each side three elongated, compressed, procumbent teeth, of which the outer, usually considered the homologue of the canine, is larger than the others. All the forms have long tails. Hind limbs not of the same disproportionate size as in the last group; and the cæcum much less developed. Tarsus but slightly elongated, the calcaneum being always less than one-fourth the length of the tibia. Toes of the hind feet free to the base. Habitat, Madagascar, and some of the adjacent Comoro Islands.

This group contains the typical Lemurs, or rather those to which the term is now chiefly restricted. Two somewhat aberrant members make it necessary to divide it into three genera.

Lemur.[644]—Upper incisors separated by an interval in the middle, and not in contact with each other or the canine, in front of which they are both placed. Muzzle elongated. Ears conspicuous and tufted. Mammæ two, pectoral. Vertebræ: C 7, D 12, L 7 (or D 13, L 6), S 3, C 27.

Animals much about the size of a common Cat, with Fox-like faces, soft thick fur, and long tails well clothed with hair. Not having the same disproportionate size of the limbs as the last group, they are much more quadrupedal in their actions, walking on the ground or running along the branches of trees on all four feet, but also jumping with marvellous agility. They are gregarious, living in small troops, are diurnal in their habits, but most active towards evening, when they make the woods resound with their loud cries. They feed not only on fruits and buds, but also on eggs, young birds, and insects. When at rest or sleeping they generally coil their long, bushy tails around their bodies, apparently for the sake of the warmth it affords. They have either one or two young ones at a birth, which are at first nearly naked, and are carried about, hanging close to and almost concealed by the hair of the mother’s belly. After a while they change their position and mount upon the mother’s back, where they are carried about until they are able to climb and leap by themselves. Though no member of the Indrisinæ has as yet lived long enough in captivity to be brought alive to Europe, various species of Lemurinæ are commonly seen in menageries, and often breed in England. They present a great tendency to variation in their colouring, in consequence of which many nominal species have been made. The most distinct, and at the same time most beautiful, is the Ring-tailed Lemur (L. catta, Fig. 328), of a delicate gray colour, and with a long tail marked with alternating rings of black and white. This is said by Mr. G. A. Shaw[645] to be an exception to all the other Lemurs in not being arboreal, but living chiefly among rocks and bushes. Pollen, however, says that it inhabits the forests of the south-west parts of Madagascar, living, like its congeners, in considerable troops, and not differing from them in its habits. He adds that it is extremely gentle, and active and graceful in its movements, and utters at intervals a little plaintive cry like that of a domestic cat. All the others have the tail of uniform colour. The largest species is L. varius, the Ruffed Lemur, sometimes black and white, and sometimes reddish-brown, the variation apparently not depending on sex or age, but on the individual. In L. macaco the male is black and the female red. L. mongoz, L. collaris, and L. albifrons are other well-known species.

Hapalemur.[646]—Upper incisors very small, subequal, separated widely in the middle line. Those of either side in contact with each other and with the canine, the posterior one being placed on the inside, and not in front of the latter. Muzzle very short and truncated. Mammæ four. There is apparently but one species, H. griseus, smaller than any of the true Lemurs, of a dark gray colour, with round face and short ears. It is quite nocturnal, and lives chiefly among bamboos, subsisting on the young shoots. A second species has been named H. simus, but it is doubtful if it is more than a variety.

Lepidolemur.[647]—Upper incisors absent or rudimentary. Muzzle more elongated than in the last. No distinct os centrale in the carpus. L. mustelinus is the best-known species. It has, at all events when adult, no upper incisors. It is rare, and like Hapalemur nocturnal in its habits. A second closely allied species, but with better developed premaxillæ, containing a pair of small styliform incisors, has been described by Peters[648] under the name of Myxocebus caniceps.

Subfamily Galaginæ.—Dentition as in Lemurinæ, from which the members of this subfamily are distinguished by the elongation of the tarsus, caused by a peculiar modification of the calcaneum and the navicular, the distal portion of the former and the whole of the latter having the form of almost cylindrical rods placed side by side, while the other bones retain nearly their normal form and proportion.

Chirogaleus.[649]—Last upper premolar very much smaller than the first molar, with only one external cusp. The animals included under this name appear to form a transition between the true Lemurs and the Galagos. The genus was originally established by Geoffroy St. Hilaire in 1812 for the reception of three species only known at that time by drawings made in Madagascar by the traveller Commerson. Subsequent discoveries have brought to light several others that may be referred to it, including one or two which are sometimes considered as forming a genus apart under the name of Microcebus. They are all small, some being less than a rat in size, long-tailed, and nocturnal in their habits. One of the largest, C. furcifer, is of a reddish-gray colour, and distinguished by a dark median stripe on its back which divides on the top of the head into two branches, one of which passes forwards above each eye. The most interesting peculiarity of these animals, a knowledge of which we owe to M. Grandidier, is that certain species (C. samati, C. gliroides, C. milii, etc.) during the dry season coil themselves up in holes of trees and pass into a state of torpidity like that of the hibernating animals in the winter of northern climates. Before this takes place an immense deposit of fat accumulates upon certain parts of the body, especially upon the basal portion of the tail, which has then dimensions corresponding to that of the well-known fat-tailed Sheep of the Cape, but which by the time they emerge from their torpor has acquired its normal proportions. The smallest species, to which many names have been given (C. pusillus, rufus, smithi, etc.), lives among the small branches on the tops of the highest trees, feeding on fruit and insects, and making nests which resemble those of birds.

Galago.[650]—Last upper premolar with two large external cusps, and nearly equalling the first molar in size. Calcaneum about one-third the length of the tibia, and the navicular much longer than the cuboid. Vertebræ: C 7, D 13, L 6, S 3, C 22-26. Tail long, and generally bushy. Ears large, rounded, naked, and capable of being folded at the will of the animal. Mammæ four, two pectoral and two inguinal.

The Galagos differ from all the Lemuroids previously mentioned, inasmuch as they are inhabitants, not of Madagascar, but of the African continent, being widely distributed in the wooded districts from Senegambia in the west to Abyssinia in the east, and as far south as Natal. They pass the day in sleep, but are very active at night, feeding on fruit, insects, and small birds. When they descend to the ground they sit upright, and move about by jumping with their hind legs, like jerboas and kangaroos. They are pretty little animals, varying in size from that of a small cat to less than a rat, with large eyes and ears, soft woolly fur, and long tails. There are several species, of which G. crassicaudatus, from Mozambique, is the largest. A similar species, or perhaps variety, from Angola is G. montieri. G. garnetti, alleni, maholi, demidoffi, and senegalensis are other recognised species. The last-mentioned was the first known to science, having been brought from Senegal by Adanson, and described in 1796 by Geoffroy, who adopted the name Galago, by which it was said to be called by the natives.

Subfamily Lorisinæ.—Dental formula as in Lemurinæ. Index finger very short, sometimes rudimentary and nailless. Fore and hind limbs nearly equal in length. Tarsus not specially elongated. Pollex and hallux diverging widely from the other digits, the hallux especially being habitually directed backwards. Tail short or quite rudimentary. Mammæ two, pectoral.

A small group of very peculiar animals, of essentially nocturnal habits, and remarkable for the slowness of their movements. They are completely arboreal, their limbs being formed only for climbing and clinging to branches, not for jumping or running. They have rounded heads, very large eyes, short ears, and thick, short, soft fur. They feed not only on vegetable substances, but, like many of the Lemuridæ, on insects, eggs, and also birds, which they steal upon while roosting at night. None of the species are found in Madagascar. One of the greatest anatomical peculiarities of these animals is the breaking up of the large arterial trunks of the limbs into numerous small parallel branches, constituting a rete mirabile, which is found also in the Sloths, with which the Loris are sometimes confounded on account of the slowness of their movements. The animals of this group are usually divided into four genera, though the characters by which they are separated are very trivial. There are more properly two natural divisions.

A. Characterised by the index finger being small, but having the complete number of phalanges, and by their Asiatic habitat.

These form the genus Loris of Geoffroy St. Hilaire (1796), Stenops of Illiger (1811), but they were in 1812 divided by Geoffroy into two genera, Nycticebus and Loris, a division which has been accepted by most modern zoologists.

Nycticebus.[651]—First upper incisor larger than the second, which is often early deciduous. Inner margins of the orbits separated from each other by a narrow flat space. Nasal and premaxillary bones projecting but very slightly in front of the maxillæ. Body and limbs stout. No external tail. Vertebræ: C 7, D 17, L 6, S 3, C 12. The species are N. tardigradus, the common Slow Lemur or Loris, of the Malay Countries, Sumatra, and Borneo; N. javanicus, of Java; and N. cinereus (Fig. 329) of Siam and Cochin China. The habits of all are much alike. They lead a solitary life in the recesses of large forests, chiefly in mountainous districts, where they sleep during the day in holes or fissures of large trees, rolled up into a ball, with the head between the hind legs. On the approach of evening they awake; and during the night they ramble among the branches of trees, slowly and quietly, in search of their food, which consists of tender leaves and fruit, small birds, insects, and mice. When in quest of living prey they move noiselessly till quite close, and then suddenly seize it with one of their hands. The female produces but one young one at a time. L. tardigradus was placed by Linnæus at the head of the list of species of his genus Lemur, and its habits doubtless suggested the generic name which was transferred by Geoffroy to the less nocturnal and spectre-like Madagascar members of the group.[652]

Loris.[653]—Upper incisors very small and equal. Orbits very large, and only separated in the middle line above by a thin vertical plate of bone. Nasals and premaxillæ produced forwards considerably beyond the anterior limits of the maxillæ, and supporting a pointed nose. Body and limbs slender. No external tail. Vertebræ: C 7, D 14, L 9, S 3, C 6. This genus is represented only by the Slender Loris (L. gracilis) of Southern India and Ceylon (Fig. 330). This species is common in some of the forest regions of Southern India, and may be purchased in the bazaars at Madras, its eyes being regarded as a remedy by the natives for ophthalmic diseases. It is a strange-looking creature, about the size of a squirrel, of a yellowish-brown colour, with large, prominent eyes, pointed nose, long thin body, long, angularly bent, slender limbs, and no tail. Its habits, according to Mr. W. T. Blanford,[654] are “very similar to those of Nycticebus tardigradus, except that the Slender Loris is rather quicker in its movements, though still slow in general. Like its ally, it is purely nocturnal and arboreal, living upon shoots and young leaves, insects, birds’ eggs, birds, and lizards. It is said to be very fond of honey or syrup. It sleeps rolled up in a ball with its head between its legs, grasping its perch with its arms.”

B. Index fingers reduced to a mere tubercle without nail. Both the known species are from West Africa.

Perodicticus.[655]—A short tail, about a third of the length of the trunk. Two or three of the anterior dorsal vertebræ have very long slender spinous processes which in the living animal project beyond the general level of the skin, forming distinct conical prominences, covered only by an exceedingly thin and naked integument. The Potto, P. potto, is one of the oldest known members of the lemuroid group, having been described in 1705 by Bosman, who met with it in his voyage to Guinea. It was, however, lost sight of until 1825, when it was rediscovered in Sierra Leone, and fully described by Bennett in 1830 under the name of Perodicticus geoffroyi. Bennett’s generic name has been retained, but the specific name bestowed by Gmelin, adopted from Bosman, has been restored. It is also found in the Gaboon. It is strictly nocturnal, and slower in its movements even than Nycticebus tardigradus, which otherwise it much resembles in its habits.

A second species, the Awantibo (P. calabarensis), rather smaller and more delicately made, with smaller hands and feet and rudimentary tail, constitutes the genus Arctocebus of Gray. It is found at Old Calabar, and is very rare, only a few individuals having as yet been met with. Vertebræ: C 7, D 15, L 7, S 3, C 9.[656]

Family Tarsiidæ.

Dentition: i ²⁄₁, c ¹⁄₁, p ³⁄₃, m ³⁄₃; total 34. The first upper incisor large, and in contact with its fellow of the opposite side. Canine of moderate size. Molars with numerous pointed cusps. Lower canine semi-erect, its apex diverging from that of the single incisor. First lower premolar smaller than those behind it. Orbit to a large extent separated from the temporal fossa by a bony partition. Fibula slender, with its lower half confluent with the tibia. Second and third digits of the hind foot with compressed claws; all the other digits of both feet with flat nails. Calcaneum and navicular bone of the foot elongated as in the Chirogales and Galagos, but to a still greater extent. Colon short and not folded. Vertebræ: C 7, D 13, L 6, S 3, C 27.

Tarsius.[657]—The family contains the single genus Tarsius, of which but one species is known, T. spectrum, the Tarsier, a very singular little animal, rather smaller than an English squirrel, with very large eyes and ears, a long thin tail, tufted at the end, and immensely elongated tarsal portion of the foot, in allusion to which its generic name was given to it. It inhabits the forests of many of the islands of the Indo-Malayan archipelago, including Sumatra, Borneo, Celebes, and some of the Philippines, feeds chiefly on insects and lizards, sleeps during the day, but is tolerably active at night, moving chiefly by jumping from place to place, an action for which the structure of its hind legs, which present a curious resemblance to those of a frog, seems particularly well adapted. It is rare, not more than two being generally found together, and only brings forth one young at a time.[658]

Family Chiromyidæ.

Dentition of adult: i ¹⁄₁, c ⁰⁄₀, p ¹⁄₀, m ³⁄₃; total 18. Incisors very large, compressed, curved, with persistent pulps and enamel only in front, as in Rodents. Teeth of cheek series with flat, very indistinctly tuberculated crowns. In the young the first set of teeth more resemble those of the normal lemurs, being i ²⁄₂, c ¹⁄₀, m ²⁄₂, all very small. Orbit surrounded by a ring of bone posteriorly, beneath which it communicates freely with the temporal fossa. Fibula well developed and distinct from the tibia. All the digits of both feet with pointed rather compressed claws, except the hallux, which has a flattened nail. Middle digit of the hand excessively attenuated. Vertebræ: C 7, D 12, L 6, S 3, C 27.

Chiromys.[659]—This family, like the last, is formed for the reception of a single genus, Chiromys,[660] containing one species, C. madagascariensis, the Aye-aye, an animal about the size of a cat, with a broad rounded head, short face, and large and naked ears. It has very large hands and long thin fingers with pointed claws, one of which (the middle or third) is remarkable for its extreme slenderness. The foot resembles that of the other lemurs in its large opposable hallux, with a flat nail, but all the other toes have pointed compressed claws, like that of the second toe in the Lemurinæ and the second and third in the Tarsiidæ. Tail long and bushy. General colour dark brown, the outer fur being long and rather loose, with a woolly undercoat. Mammæ two, inguinal in position. It is a native of Madagascar, where it was discovered by Sonnerat in 1780. The specimen brought to Paris by that traveller was the only one known until 1860. Since then many others have been obtained, and they may frequently be seen living in the gardens of the Zoological Society of London. Like so many of the Lemurs, the Aye-aye is completely nocturnal in its habits, living either alone or in pairs, chiefly in the bamboo forests. Observations upon captive specimens have led to the conclusion that it feeds principally on succulent juices, especially of the sugar-cane, which it obtains by tearing open the hard woody circumference of the stalk with its strong incisor teeth. It is said also to devour certain species of wood-boring caterpillars, which it obtains by first cutting down with its teeth upon their burrows, and then picking them out of their retreat with the claw of its attenuated middle finger. It constructs large ball-like nests of dried leaves, lodged in a fork of the branches of a tree with the opening on one side. The resemblance of its teeth to those so characteristic of the Rodentia caused it to be placed formerly in that order, and it was only when its anatomical characters were fully known that its true affinities with the Lemurs became apparent.[661]

Extinct Lemuroids.

The discoveries of the last few years have revealed the former existence, both in Europe and North America, of a number of extinct animals more or less closely allied to the living Lemurs, which are of especial interest as showing in some instances characters of a more generalised type than is the case with the living representatives of the suborder. It is, however, in some cases very difficult to determine whether these extinct forms should be referred to the Lemuroidea or Insectivora; and if those naturalists are right who regard these groups as survivors of a very generalised ancestral type of mammalian organisation, it is to be expected that as we recede in time we should find that the two groups show more and more marked signs of a natural connection. The earliest reference of one of these extinct Upper Eocene types to the Primates was made in 1862 by Professor L. Rütimeyer, of Basle, who described part of an upper jaw with three teeth from the so-called Bohnerz of Egerkingen, near Soleure in Switzerland, under the name of Cænopithecus lemuroides, regarding the animal to which the specimen belonged as partaking of the characters both of the Lemurs and the American Monkeys. Most other palæontologists refused, however, to accept this determination, and it was not until many years later that the researches of Gaudry and Filhol showed not only that Cænopithecus was indeed a true Lemuroid, but also that it was either identical with or closely allied to a form described by Cuvier in the early part of this century under the name of Adapis and regarded as referable to the Ungulata. Later researches have brought to light other Lemuroids in the Tertiaries of both the Old and the New World; and it is very noteworthy that all these types seem to have disappeared from both regions with the close of the upper portion of the Eocene period.

Among the more interesting of the forms which are generally regarded as true Lemuroids we may first mention a small species from the Quercy Phosphorites, of which the hinder cheek-teeth are shown in Fig. 332, A, which was originally described as Necrolemur antiquus, but appears to be generically identical with Microchœrus erinaceus, of the upper Eocene of Hampshire, of which the corresponding teeth are shown in B of the same figure. In this genus, according to Dr. Schlosser, the dental formula is i ²⁄₁, c ¹⁄₁, p ³⁄₃, m ³⁄₃, or the same as in the existing Tarsius; but it is not improbable that in some instances the first lower premolar may have been developed. The upper molars of M. erinaceus differ from those of M. antiquus by the simpler structure of their columns and the smaller size of the external cingulum, which lacks the median cusp found in the latter. The angle of the mandible is produced into a large hook-like flange which at once distinguishes the genus from all existing Lemurs; and the anterior lower premolar is not canine-like. M. antiquus is of very small size, but the larger M. edwardsi of the same deposits comes nearer in dimensions to M. erinaceus. The upper molars decrease in size from the first to the third, the first and second having a median cusp in the external cingulum, by which they are readily distinguished from the corresponding teeth of the under-mentioned genus Hyopsodus. The third upper molar differs from that of Hyopsodus by its small size and the abortion of its posterior columns. The skull approximates to that of the living genus Galago, exhibiting the same inflation of the auditory bulla. The upper molars are also not unlike one species of that genus, but the fourth upper premolar has but one outer cusp, as in Chirogaleus.

The small Anaptomorphus, from the North American Eocene, has a skull of about the same size as that of the smallest species of Microchœrus, but the dental formula is i ²⁄₂, c ¹⁄₁, p ²⁄₂, m ³⁄₃, and the upper molars are of the tritubercular type.

The well-known Adapis (Aphelotherium or Palæolemur), of the Upper Eocene of France and England, differs from all existing Lemuroids in possessing four premolars[662]; the dental formula being i ²⁄₂, c ¹⁄₁, p ⁴⁄₄, m ³⁄₃. The fourth upper premolar has two outer cusps, and the upper molars (Fig. 333) resemble those of Lepidolemur and Hapalemur, while the lower canine is a well-developed tooth performing the usual function of biting against the canine of the upper jaw. The lower incisors have upright, spatulate crowns, as in the true Apes. The skull is said to approximate in contour to that of Propithecus. The typical A. parisiensis is of comparatively small size, but the species of which the upper cheek-teeth are shown in the woodcut is of much larger dimensions. The skull of A. magna, which measures upwards of 4 inches in length, resembles that of A. parisiensis in its general characters, but is modified much in the way that the skulls of larger animals differ from the smaller ones of the same natural group. Thus the brain-chamber and orbits are relatively smaller, the face larger, the muscular crests more developed, and the constriction between the cerebral and the facial portion of the skull more marked. These modifications remove the skull in its general characters still farther from the existing Lemurs—so much so that M. Filhol refers it and the other species of Adapis to a distinct zoological type, intermediate between the lemurs and the pachyderms, to which he gives the name of Pachylemuriens, but later researches do not support this view. As mentioned above, it has been suggested that Cænopithecus lemuroides is inseparable from Adapis parisiensis, but the postero-internal column of the upper molars is said to be larger. The genera Tomitherium and Notharctus, of the Eocene of the United States, appear to be allied to Adapis, but the second has a larger lower canine. The same deposits have also yielded more or less imperfect remains of other forms departing more widely from the existing Lemuroid type. Of these Hyopsodus, of the Wasatch and Bridger Eocene of the United States, has the dental formula i ²⁄₂, c ¹⁄₁, p ⁴⁄₄, m ³⁄₅. The quadrituberculate upper molars have well-developed accessory intermediate columns (protoconule and metaconule), and thus resemble those of Microchœrus; the external surfaces of the outer columns of their teeth being flattened, with vertical ridges and a distinct cingulum. The third upper molar has its postero-internal column (hypocone) partly aborted, but is otherwise as well developed as the preceding molars. Microsyops, of the North American Eocene, appears to have been an allied form in which there were probably only three premolars.