THE DRILL.

Papio leucophæus.---F. CUVIER.

PLATE XVIII.

Le Drill, Frederic Cuvier, Histoire Naturelle des Mammiferes. Cynocephale drill, Cynocephalus leucophæus, Desmarest's Mammalogie, p. 71.

THE Drill is nearly as strong and powerful as the Mandril, and has a similar form. The colours of the adult are also nearly alike, generally of a duller hue; but the principal distinguishing character is the absence of the ridges upon the muzzle, and of bright colouring except the border of the upper lip, which, by Fred. Cuvier, is represented of a bright red. The under parts are also white. The female differs in a less size and duller colouring, and by the head being of a shorter proportion. The native country seems somewhat uncertain, but it most probably is also Africa.

With these animals, the forms of the Old World terminate; and we now commence the second great geographical division of the quadrumanæ.

THE MONKEYS OF SOUTH AMERICA; OR, THOSE OF THE NEW WORLD.

THE forms contained in this division are almost entirely confined to the tropical regions of the Southern Continent.* They differ in a remarkable degree from all those we have described in the previous part of this volume, and in no instance can the South American species be classed with the inhabitants of the Indian or African Continents. The most striking outward differences, are the smaller size and less ferocious manners of the greater number, the prehensile tail of many, and the want in all of the cheek-pouches and naked callosities. Internally, the larynx is remarkable for its great developement, and the teeth are thirty-six instead of thirty-two, and, besides, differ considerably in their structure, as will be perceived in the woodcuts we have introduced.

In the arrangement of this geographical group, we have followed that of Geoffroy Saint Hilaire, with the exception of placing the howlers (Mycetes) first, as the

* Named Platyrrhini by Geoffroy.

Baron Cuvier has done, instead of Ateles, and of following them by that genus, and Cebus of Xerleben.

THE HOWLERS

contain a single genus, named by Illiger Mycetes,* from the remarkable howling voice of the animals. It is characterised by a facial angle of about 30°; the tail very long, naked at the extremity, and prehensile. The dentition, according to Frederic Cuvier, is nearly similar in this and the two next genera; and we add the delineation which he considers typical of these

forms. But the prominent character in this group is the extraordinary developement of the larynx, which is ventricose, and appears on the outside in the form of

* Muxnτns, howling.

a swelling. The internal structure of this member, in the Mono colorado of Humboldt, is thus described in his Zoological Observations, and will serve as a model for the others. "The bony case of the os hyoides, measured by water, gave a size equal to four cubic inches; the larynx was slightly attached by muscular fibres, and communicated by a membranous canal. The larynx consisted of six pouches of ten lines in length, to from three to five in depth. These pouches resemble those of the small whistling monkeys, squirrels, and some birds. They have an opening above on the same side with that of the glottis, by which the air cannot enter without shutting the epiglottis. Above the pouches there are two others, of which the lips or borders are yellowish. These are the pyramidal sacks which enter into the bony case, and are formed by membranous partitions. The air is driven into these sacks, which are from three to four inches long, and terminate in a point, but come in contact with no part of the large hyoid bone opening below. The fifth pouch is found in the opening of the arythenoid cartilage, and is situated between the pyramidal sacks of the same form, but shorter; and the sixth pouch is formed by the bony drum itself, within which the voice acquires the mournful and plaintive tone which characterises these animals."

* Humboldt, Zool. Observ. I. p. 9.

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