| Fig. 1. Lemuroid Ear. | Fig. 2. Anthropoid Ear. |
The trunk is relatively long and compressed, and the tail when long is never truly prehensile. Of the limbs, the posterior are longer than the anterior, and all have five digits, each bearing a flat nail except the second toe, which has invariably a long pointed claw, their tips ending in prominent discoidal tactile pads. (Fig. 3.)
Of the digits, the index is sometimes quite rudimentary, while the thumb is large, and the great toe especially so, both being opposable. Teats occur on the breast, on the abdomen, or on both.
Of the skeleton, the eye-sockets, or orbits, are directed forward, and have complete bony margins, which, however, are not closed in by bone behind (as in Monkeys), but freely communicating beneath the post-orbital process (except in Tarsius) with the temporal hollow behind. In the young of some species the orbit is more enclosed than it is in the adult: the orifice for the lachrymal duct of the eye is placed external to the margin of the orbit: the hollow for the olfactory lobes of the brain is always large.
Fig. 3. Foot of Chirogale trichotis, Günther.
(P. Z. S., 1875, p. 79.)
Having four kinds of teeth, and a set in succession to the milk-teeth, they are Heterodont and Diphyodont. The dental formula is I22, C11, P33, M33 = 36 (vide anteà, p. [6]), and the upper jaw has a toothless space in the centre (except in the Aye-Aye). Of the upper teeth, the incisors are sometimes absent, but generally present; if unequal in size the inner one is the larger of the two. The canines are prominent; the pre-molars all have a cingulum, or girdle, round the base, more or less enlarged backwards into a process ("talon" or "heel"); the anterior pre-molar vertically long and canine-shaped; the median and posterior with three main points (tubercles or cusps) and one or two smaller ones on the crown, and having a bar or ridge uniting the front inner with the hind outer cusp. The anterior and median molars have three or four main cusps, and one or two smaller or subsidiary ones on the crown; the cingulum is well developed. The posterior molars have generally three cusps.
In the lower jaw the incisors are close-set and comb-like, remarkable for protruding in front, like the teeth of a Rat or a Rabbit. The canines also protrude horizontally, and, being placed alongside of the incisors, are difficult to distinguish from the latter excepting that they are broader and thicker.
| Fig. 4. Skull of Lemuroid. From Blanford's "Mammalia of British India" (by permission of the author). | Fig. 5. Skull of Anthropoid. From Blanford's "Mammalia of British India" (by permission of the author). |
Of the pre-molars the anterior are canine-shaped, the median and posterior ones have three main, and one or two subordinate, cusps on the crowns. In both the upper and lower molars, cross-bridges stretch between the outer and inner front cusps as well as between the outer and inner hind cusps. There is an oblique ridge between the hind outer and the front inner cusp, and another is often present between the front outer cusp and the anterior "heel," producing, as Huxley has pointed out, almost a double crescentic pattern, as in many lower Mammals. The posterior molar has four or five cusps.