This family, like the preceding, has been constituted for the reception of two animals which are so remarkably distinct from all the other species of Lemurs, as to necessitate their being thus segregated. Between these two forms however, so close a relationship exists, that they have often been considered as only varieties of the same species. The family, therefore, consists, as in the _Chiromyidæ_, of a single genus, the characters of which constitute also those of the family. THE TARSIERS. GENUS TARSIUS. _Tarsius_, Storr. Prod. Method. Mamm., p. 32 (1780). The Tarsiers are distinguished externally by the possession of a rounded head, and a very short, pointed muzzle; by their very large, long and naked ears, and eyes so remarkably large and protruding, as to form the most prominent feature of the face. The hind-limb, which is much longer than the fore-limb, is also very remarkable on account of the great elongation of the ankle-region (or tarsus) of the limb. The long and slender toes terminate in round, sucker-like discs, and are furnished with flat nails, except on the second and third toes, where the nails are merely compressed claws. The {19}fore-limb, with or without the hand, is longer than the trunk; its digits also are long and slender (the third being longest, and the second equal to the fourth) and, like those of the foot, terminate in round sucker-like discs. Both the wrist and ankle are haired. The long and Rat-like tail is longer than the body, and has a tufted termination. The skull presents enormous eye-cavities, the inner margins of the latter almost meeting in the centre. The orbits are nearly closed in from the temporal fossa by the union of the malar and alisphenoid bones--a character in which they differ from all other Lemurs, and approach the Anthropoid section of the Primates. Their dental formula is I2/1, C1/1, P3/3, M3/3 = 34. Of the upper jaw, the incisors are prominent and unequal, the anterior ones being larger than the posterior, and in contact in the middle line, thus leaving no central gap in the front of the jaw, as is the rule among Lemurs; the canines are about as long vertically as the inner incisor, and are smaller than the corresponding tooth in the True Lemurs; the pre-molars are canine-like, sharp, pointed, and furnished with a cingulum; the anterior pre-molar is smaller than the two others; the posterior pre-molar has one external and one internal cusp; the molars, all nearly equal in size, are wide transversely, strongly cingulate, and have two prominent external cusps. In the lower jaw, the solitary incisor in each half is small, and, instead of protruding horizontally, is nearly erect; the canines are also almost erect, and less like incisors than is usual in the Sub-order. The pre-molars are sharp, but the anterior is smaller than the two posterior; the anterior and median molars have four cusps, and are cingulate, while the posterior molar has five cusps.