_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.
{20}The Tarsiers have nineteen dorsal and lumbar vertebræ together, and
twenty-seven in the tail. The humerus presents a perforation (the
entepicondylar foramen) at its lower inner side, and another nearly in the
centre above the hinge. The femur is more than twice the length of the
arm-bone; the lower half of the slender fibula is co-ossified with the
tibia, while two of the tarsal, or ankle-bones (the _calcaneum_ and
_naviculare_), are remarkably elongated, thus giving to the hind-limb of
these animals the singular conformation from which they derive their name.
The large intestine is not convoluted upon itself as in so many of the
Lemurs, nor is there a cæcum at the junction of its smaller and larger
portions.