Macacus cyclopis, Swinh., P. Z. S., 1862, p. 353, pl. xiii., 1864, p. 380; Sclater, P. Z. S., 1864, p. 711 (woodcut); Anderson, Zool. Exped. Yun-nan, p. 87 (1878; with synonymy).
Macacus sancti-johannis, Gray, Cat. Monkeys, Brit. Mus. App., p. 129 (1870; in part); Scl., P. Z. S., 1871, p. 222.
Macacus rhesus, Scl., P. Z. S., 1871, p. 222.
Macacus erythræus, pt. Schl., Mus. Pays-Bas, vii., p. 112 (1876).
Characters.—Allied to M. rhesus, but the head round; the face flat, and round; supra-orbital region bare, as in other species; cheeks dark-whiskered; ears small and haired; a strong ruff-like beard; tail stout, thickly haired and tufted, 12 inches long. Fur thick and woolly; hair behind the mouth, and below and behind the ears ringed; hair not longer on the shoulders than on the rest of the body.
General colour olive-grey, or slaty; the hairs finely freckled with yellow; no rufous on the lower back and hind quarters; legs dark, and a distinct black line along the top of the tail.
The characters of the head, face, whiskers, beard, and the thick tail, and the absence of the rufous colour distinguish it from M. rhesus. M. assamensis is redder than M. rhesus or M. cyclopis, and has a long head, projecting face, and a short tail.
Female.—Smaller and rather lighter coloured than the male. At the love-period the naked posterior parts with the thighs and tail become excessively swollen, and florid.
Distribution.—The island of Formosa, where it is the only known species of Monkey.
Habits.—The late Consul Swinhoe was the discoverer of this interesting animal. He has given an account of its habits in the "Proceedings of the Zoological Society," from which we quote the following: "The Formosan Rock-Macaque affects rocks and declivities that overhang the sea, and in the solitary caverns makes its abode. On the treeless mountain in the south-west, called Apes' Hill, it was at one time especially abundant, but has since almost entirely disappeared. About the mountains of the north and east it is still numerous, being frequently seen playing and chattering among the steep rocks, miles from any tree or wood. It seems to be quite a rock-loving animal, seeking the shelter of caves during the greater part of the day, and assembling in parties in the twilight, and feeding on berries, the tender shoots of plants, Grasshoppers, Crustacea, and Mollusca. In the summer it comes in numbers during the night, and commits depredations among the fields of sugar-cane, as well as among fruit-trees, showing a partiality for the small, round, clustering berries of the Longan (Nephelium longanum). In the caverns among these hills they herd; and in June the females may frequently be seen in retired parts of the hills with their solitary young one at their breasts. These animals betray much uneasiness at human approach, disappearing in no time, and skulking in their holes till the intruder has passed. They seem, too, to possess abundance of self-complaisance and resource; for I have frequently seen a Monkey seated on a rock by himself, chattering and crying merely for his own amusement and gratification. Whatever Mr. Waterton may say of the tree-loving propensity of Monkeys in general, it is very certain that this species shows a marked preference for bare rocks, covered only with grass and bush; for if he preferred the forest he might very easily satisfy his desire by retiring a few miles further inland, where he could find it in abundance. But, on the contrary, in the forest he is only an occasional intruder, resorting thither when food fails him on the grassy hills by the sea, where he loves to make his home. The Chinese have a fanciful idea that the tail of the Monkey is a caricature of the Tartar pendant into which they twist their long black hair, and they invariably chop it off any Monkey that comes into their possession. Hence the difficulty of procuring Monkeys in China with perfect tails."