Part 7

Among the Lorisinæ the dorsal and lumbar vertebræ together number from twenty-one to twenty-three. The cæcum, at the junction of the larger and smaller intestine, is long. The main artery of the fore- and hind-limbs breaks up into a rete mirabile of numerous small parallel branches.

The Slow-Lemurs are distributed in the western parts of the African continent, and in the Indian, Malayan and Indo-Chinese portions of the Oriental region. It is a remarkable fact that this group should be confined to one portion of Africa and be entirely absent from Madagascar, the country where the Lemurs form so characteristic a feature in the fauna.

The Lorisinæ embrace three genera, the Pottos (Perodicticus) from the African continent; the Slender Loris (Loris), and the Slow-Loris (Nycticebus), both of which inhabit the Oriental region.

{26}THE POTTOS. GENUS PERODICTICUS.

Perodicticus, Bennett, P. Z. S., 1839, p. 109; Huxley, P. Z. S., 1864, p. 235.

Arctocebus, Gray, P. Z. S., 1863, p. 150; Mivart, P.Z.S., 1864, p. 644.

This genus contains two species, both confined to the West Coast of Africa. The Pottos are slender-bodied animals, with oval heads and blunt Dog-shaped muzzles. Their eyes are large and full, and their external ears erect, with shelf-like lamellæ inside. They have slender and sub-equal limbs. The second digit of the fore-limb is rudimentary and nail-less; it is supported on one wrist-bone, and has two phalanges or finger-bones. The great toe is opposable, and the fourth and fifth digits of both limbs are united together by membrane as far as the first joint. The processes of the vertebræ in the neck and back are long and protruding. The tail is very short.

The pre-maxillæ (which carry the incisor teeth) do not project in front, nor does the bony palate extend farther back than the end of the posterior molar teeth. Of the upper teeth the incisors are equal in size (Fig. 6); the median and posterior pre-molars have on their crowns three cusps, of which the two outer are the larger; the anterior and median molars are cingulate, have four-cusped crowns, and are larger than the pre-molars; the posterior is narrow from before backwards, and its crown presents only two or three cusps. Of the lower teeth, the anterior pre-molar is recurved and larger than the canine, with a ridge on its inner face and a cusped heel behind; the median and posterior ones are shorter than their anterior fellow, each having a strong posterior cusped heel; the anterior and median {27}molars have their crowns four-cusped and are nearly equal in length; the crown of the posterior molar is 4-5-cusped, and has a ridge joining its anterior heel to its front outer cusp. Transverse and oblique ridges are well marked on the crowns of both the upper and lower cheek-teeth.

I. THE CALABAR POTTO. PERODICTICUS CALABARENSIS.

Perodicticus calabarensis, Smith, Proc. Roy. Phys. Soc., Edinb., 1860, p. 172, figs. 1, 2.

Arctocebus calabarensis, J. E. Gray, P. Z. S., 1863, p. 150; Huxley, P. Z. S., p. 314, pl. 28 (1864).

Nycticebus calabarensis, Schlegel, Mus. Pays Bas, vii., p. 287 (1876).

CHARACTERS.--Hair long, wool-like; face, hands, and feet thinly haired. Head 2½ inches long, tapering in front; muzzle prominent and blunt; ears large, pointed, and projecting above the level of the head, with short hairs, two lamellæ inside, and marginal tufts; neck short; hind-limbs slightly larger and {28}longer than the fore-limbs; hands smaller than the feet; thumb thick, with a tubercle at base; the wrist-bone of the very rudimentary index-finger supporting two rudimentary finger-bones; third finger not parallel to fourth and fifth; the fourth longest (Fig. 7). Great toe with a tubercle at its base, opposable. Tail ¼ inch long, hidden in the fur of the body.

Fur grey at base of hairs, fawn-coloured farther up, and tipped with dark brown, uniform over the body and limbs; face darker; sides of head lighter; line from brow down the nose white. No vibrissæ on face and no eyebrows; chin, throat, inner surface of limbs, and under side of body, greyish-white.

Posterior upper molar nearly equal to posterior pre-molar, with the hind inner cusp of the crown rudimentary. Lower incisors not visible beyond the lip, cingulate; posterior molar five-cusped and relatively larger than in the next species (P. potto). Bony palate with large perforations behind the incisors. Intestines, 40 inches long; cæcum, 2½ inches.

DISTRIBUTION.--The "Angwantibo," as this species is called, is known only from Old Calabar, on the west coast of Africa.

II. BOSMAN'S POTTO, PERODICTICUS POTTO.

Potto, Bosman, Beschrijving van de Guinese Goudkust, ii., p. 32, fig. 4 (1704).

Nycticebus potto, Geoffr., Ann. Mus., xix., p. 165 (1812); Schlegel, Mus. Pays Bas vii., p. 287 (1876).

Perodicticus geoffroyi, Bennett, P. Z. S., 1830, p. 109.

Perodicticus potto, V. der Hoeven, Tijdschr. v. Natuurl. Gesch., xi., p. 41 (1844); Wagner, in Schreber's Säugeth. Suppl., v., p. 183 (1855).

Stenops potto, Pel, Bijdragen tot de Dierkunde, 1852, p. 41.

CHARACTERS.--More common than the Angwantibo and {29}distinguished from it by its rounder, shorter, and wider head, less produced muzzle, smaller mouth, and eyes farther apart; ears shorter, rounder, and directed more backwards, with one lamella on the inner surface. Hands longer, flat and thin; index-finger not so reduced as in P. calabarensis. Tail very short, little more than an inch long, but visible beyond the fur. Length of body, 8 inches.

Upper pre-molars less canine-like than in the preceding species; posterior upper molar differing in size from and set farther out than the others, short and wide, with the crown elliptical and only two-cusped, the two hind-cusps wanting. Lower incisors more prominent and projecting than in P. calabarensis; crown of posterior lower molar four-cusped.

ADULT.--Upper surface rich reddish-brown with a black dorsal stripe widening opposite the shoulders, and fading out towards the tail; under side yellowish or reddish-white. Hair on face shorter and paler, with a dark ring round the eyes.

YOUNG.--Reddish-brown all over, redder on the back of the head and neck, darker on the shoulders; creamy-white, washed with rufous, beneath.

Fur silver-grey at the base of the hairs, with reddish-brown tips in younger, and dark golden-brown in older, individuals.

DISTRIBUTION.--The Potto is one of the oldest known members of the Lemuroid group, having been described in 1704 by Bosman, who met with it on his voyage to Guinea. It was, however, lost sight of until 1825, when it was rediscovered in Sierra Leone and fully described by Bennett in 1830. It is known also from Gaboon.