FAMILIES OF THE SUB-ORDER LEMUROIDA AND THEIR GENERA.[145]

Genera.
Family I.—Lemuridæ Indris.
Lepilemur.
Lemur.
Hapalemur.
Cheirogale.
Galago.
Family II.—Nycticebidæ Perodicticus.
Loris, or Stenops.
Nycticebus.
Arctocebus.
  „ III.—Tarsidæ Tarsius.
  „ IV.—Cheiromydæ Cheiromys.

As groups these have more or less well-defined differences. Thus, the Lemuridæ have no rete mirabile, and, except in one species, the tail is large, and all have their hind legs longer than their front ones.

The Nycticebidæ have short ears and faces, and the tail is short or absent. They have a strange defect in the fingers (of hand and foot), the ankle is short, and there is a rete mirabile.

As a family the Tarsidæ have long ears, a long ankle, a long and slender tail, and there is a rete mirabile. Moreover, the fourth finger is not the longest.

The Cheiromydæ are known at once by their great front teeth, and the probe-like middle finger of the hand.

GEOGRAPHICAL DISTRIBUTION.

All the kinds of Indris, Lepilemur, Hapalemur, Lemur, and Cheirogale inhabit Madagascar and some of the small islands close to its coast, and one kind of Lemur is found in one if not in two of the Comoro Islands, which are between the north west of Madagascar and the African coast, and nearer the island than to the continent. They have not been discovered elsewhere, and this is extremely interesting, because, with the exception of the genus Galago, they form the entire family of the Lemuridæ. The Galagos are not found in Madagascar, but in the woods and forests of the opposite coast of Africa. Some Galagos are found as far south as Port Natal, and the thick-tailed species inhabits both the eastern and the western coasts of the continent, and the central parts also. Others have been found near the Gaboon and in Fernando Po, Senegal, and Gambia, and in the country of Sennaar and near the White Nile. The Aye-Aye is essentially a Madagascar form. The Nycticebidan family has a wide geographical range. Thus, the species of the genus Loris are found in Ceylon, in Southern India at Pondicherry, and in Hindostan; the genus Nycticebus has one species in Borneo and Sumatra, a second in Java, and a third in China. On the contrary, the remaining genera, Perodicticus and Arctocebus, are limited to the west coast of Africa, none of them being found in the intermediate regions of that continent or in Madagascar. Finally, the Tarsidæ, according to Wallace, inhabit Borneo, Celebes, and some other neighbouring islands, the species being the same in all localities. How is the widespread distribution of the animals of the sub-order to be explained? On the presumption that they all sprang from one parent stock, it is necessary to suggest the occurrence of vast geographical changes in bygone ages, such, for instance, as the former connection of Madagascar and the mainland of Africa, and their separation; the former existence and subsequent subsidence of a vast tract of land between Hindostan and Africa, north of and remote from Madagascar; and the former continuity of land where there are now the islands of Borneo, Sumatra, and Java. It is necessary also to assume that Ceylon was united to Hindostan; and the great islands just mentioned to the continent of Asia. The land which was intermediate between Hindostan and Africa has been called Lemuria by Dr. Sclater, and its theoretical existence explains the otherwise incomprehensible presence of Giraffes and Hippopotami, now purely African genera, in the olden time in Asia. Geology rather favours these views. The first Lemuroida swarmed amongst the forests of these vast countries, and their descendants cut off from each other by geographical changes are now limited to very remote localities.

The fossil remains of Lemuroida, or of animals whose skulls resemble somewhat those of the sub-order, have been found in the Eocene of the Western territories, of the United States, and also in the south of France.