452 Zoological Society. 



the black species of the Amazon, however, are of the same colour in 

 both sexes. The species of this genusj are seminocturnal in their 

 habits, uttering their cries late in the evening and before sunrise, and 

 also on the approach of rain. Humboldt observes, that the tremen- 

 dous noise they make can only be accounted for by the great num- 

 bers of individuals that unite in its production. My own observa- 

 tions, and the unanimous testimony of the Indians, prove this not to 

 be the case. One individual only makes the howling, which is cer- 

 tainly of a remarkable depth and volume and curiously modulated ; 

 but on closely remarking the suddenness with which it ceases and 

 again commences, it is evident that it is produced by one animal, 

 which is generally a full-grown male. On dissecting the throat, much 

 of our wonder at tbe noise ceases ; for besides the bony vessel formed 

 by the expanded "os hyoides," there is a strong muscular apparatus 

 which seems to act as a bellows in forcing a body of air through the 

 reverberating bony cavity. 



Of the genus Ateles, the four-fingered Spider Monkeys, one species 

 is found only in the Guiana district, north of the Amazon and Rio 

 Negro. Another, probably Ateles ater, inhabits the West Brazil 

 district on the river Purus. These monkeys are slow in their mo- 

 tions, but make great use of their prehensile tail, by which they 

 swing themselves from bough to bough ; and I have been informed 

 that two have been seen to join together by their hands and prehen- 

 sile tails, to form a bridge for their young ones to pass over. The 

 Indians also say, that this animal generally moves suspended beneath 

 the boughs, not walking on them. 



The next genus, Lagothrix, is a very interesting one, being quite 

 unknown in Guiana and Eastern Brazil. The species I am acquainted 

 with (L. Humboldtii) is found in the district south-west of the Bio 

 Negro, towards the Andes, which I call the Ecuador district of tbe 

 Amazon. They are remarkable for their thick woolly grey fur, their 

 long prehensile tails, and very mild disposition. In the upper Ama- 

 zon they are the species most frequently seen tame, and are great 

 favourites, from their grave countenances, more resembling the human 

 face than those of any other Monke} r s, their quiet manners, and the 

 great affection and docility they exhibit. I had three of them for 

 several months before leaving Brazil, and they were on board with 

 me at the time the ship was burnt, when, with their companions, they 

 all perished. 



The Sapajou Monkeys, forming the genus Cebus, appear to be 

 more generally distributed, and the species have a wider range. 

 They are also frequently domesticated, but offer a remarkable con- 

 trast to the species of the last genus, in their constant activity and 

 restlessness, and they have the character of being the most mis- 

 chievous monkeys in the country. 



Each species of the genus BracJiyurus appears to be confined to a 

 particular district. The B, couxiu is a native of Guiana, and does 

 not pass the Rio Negro on the west, or the Amazon on the south. 

 The B. ouakari is found on the Upper Rio Negro ; the B. rubi- 

 cundus on the Upper Amazon, called the Solimoes ; and another 



