All the Malagasy lemurs, which agree in the structure of the internal ear, are now included in the family Lemuridae, confined to Madagascar and the Comoro Islands, which comprises the great majority of the group. The other families are the Nycticebidae, common to tropical Asia and Africa, and the Tarsiidae, restricted to the Malay countries.
The gentle lemurs (Hapalemur) have a rounder head, with smaller ears and a shorter muzzle, and also a bare patch covered with spines on the fore-arm.
The sportive lemurs (Lepidolemur) are smaller than the typical species of Lemur, and the adults generally lose their upper incisors.
The typical lemurs include species like Lemur mongoz and L.
Like the gentle lemurs they are nocturnal.
The foot resembles that of the other lemurs in its large opposable great toe with a flat nail; but all the other toes have pointed compressed claws.
Like so many lemurs, it is completely nocturnal in its habits, living either alone or in pairs, chiefly in the bamboo forests.
Till recently the aye-aye was regarded as representing a family by itself - the Chiromyidae; but the discovery that it resembles the other lemurs of Madagascar in the structure of the inner ear, and thus differs from all other members of the group, has led to the conclusion that it is best classed as a subfamily (Chiromyidae) of the Lemuridae.
SIFAKA, apparently the name of certain large Malagasy lemurs nearly allied to the Indri but distinguished by their loiig tails, a:id hence referred to a genus apart - Propithecus, of which three species, with several local races, are recognized.
In disposition they are quiet and gentle, and do not show much intelligence; they are also less noisy than the true lemurs, only when alarmed or angered making a noise which has been compared to the clucking of a fowl.
In organization the tarsier departs markedly from other lemurs as regards several particulars, and thereby approximates to monkeys and apes.
No lemurs occur, although a species is found in Assam, and another in southern India.
The projection of the muzzle, which gives the character of brutality to the gorilla as distinguished from the man, is yet further exaggerated in the lemurs, as is also the backward position.
A series of the apes, arranged from lower to higher orders, shows gradations from a brain little higher that that of a rat, to a brain like a small and imperfect imitation of a man's; and the greatest structural break in the series lies not between man and the manlike apes, but between the apes and monkeys on one side, and the lemurs on the other.
First, the Anthropini, consisting of man only; second, the Catarhini or Old World apes; third, the Platyrhini, all New World apes, except the marmosets; fourth, the Arctopithecini, or marmosets; fifth, the Lemurini, or lemurs; sixth and seventh, the Cheiromyini and Galeopithecini.
In other instances, notably in the lemurs, but also in certain carnivora, rodents and marsupials, they occupy a position on the fore-arm near the wrist, in connexion with glands, and receive sensory powers from the radial nerve.
In some mammals, notably lemurs, occurs a hard structure known as the sublingua, which may terminate in a free horny tip. If, as has been suggested, this organ represents the tongue of reptiles, the mammalian tongue will obviously be a superadded organ distinctive of the class.
Prosimiae (Lemurs and Galagos).
As regards the latter order, although we are at present unacquainted with all the connecting links between the lemurs and the monkeys, there is little doubt that the ancestors of the former represent the stock from which the latter have originated.
Till recently the galagos have been included in the family Lemuridae; but this is restricted to the lemurs of Madagascar, and they are now classed with the lorises and pottos in the family Nycticebidae, of which they form the section Galaginae, characterized by the great elongation of the upper portion of the feet (tarsus) and the power of folding the large ears.
The main facts at the present day are, firstly, the restriction of the Prosimiae, or lemurs, to the warmer parts of the Old World, and their special abundance in Madagascar (where other Primates are wanting); and, secondly, the wide structural distinction between the monkeys of tropical America (Platyrrhina), and the Old World monkeys and apes, or Catarrhina.
It is, however, noteworthy that extinct lemurs occur in the Tertiary deposits of both halves of the northern hemisphere - a fact which has induced Dr J.
Earle, in the American Naturalist for 1897, observes that " so far as the palaeontological evidence goes it is decidedly in favour of the view that apes and lemurs are closely related.
In regard to Tarsius, it is evidently a type nearly between the lemurs and apes, but with many essential characters belonging to the former group."