THE MONKEYS OF THE NEW WOULD. 
203 
the junction of the hind third with the two fore thirds of the length of the brain. They have nume- 
rous vertebrae in their back-bone, and those in the back and loins number usually nineteen. It is 
stated by Cuvier that there is an air sac in the neck of the Midas Ursulas , which communicates with 
the organ of voice through a space between two of its cartilages. It appears that the hands and 
feet of the Marmosets have thumbs and toe-thumbs so slightly separable from the fingers and toes that 
the resemblance to “ feet” is decided. This is ind eased by the fact that the thumbs ha^e claws on 
them, and the toe-thumb is the only digit with a flat nail, all the rest having claw-like ones. The thumb 
is really not opposable, but nevertheless the muscles are there to give it movement ; the opponens 
muscle of the thumb is doubtfully present, but the adductors, abductor, and long and short flexors are 
all there. There is much union of the deeper muscles of the fingers, indicating less independence of 
.movement. In the foot the toe-thumb has no special abductor, and the transversus pedis is absent. 
CHAPTER XIII. 
GENERAL REMARKS ON THE QUADRUMANA. 
The Classification of the Monkeys of the New World — The Geographical Distribution of the Genera — The Fossil Monkeys oi 
the New and Old World and their Alliances — The former old Fauna of Europe, Asia, and Africa — The Resemblance of 
Quadrumana to other Animals and Man. 
With regard to the Monkeys of the New World, they are to be grouped and classified as follows : — 
The Howlers must be placed by themselves, then the Spider Monkeys ; the Lagotriches and the 
Sajous form a very distinct group ; and thus the prehensile-tailed series is complete. Then come the 
non-prehensile-tailed. The Sakis form one group, and the Squirrel Monkeys, and the Night, or Owl 
Monkeys (the Douroucoulis), make a second. The Arctopithecini are another family, and consist of 
the Marmosets and Tamarins. 
Family. 
Sub-Family . 
Genus. 
/ Mycetes .... 
Example. 
Howler. 
Platyrhini, or Cebidse 
. Prehensile-tailed 
l Ateles ..... 
) Lagothrix .... 
' Cebus ..... 
/ Pithecia, including Brachyurus 
\ Callithrix .... 
\ Nyctipithecus 
Spider Monkey. 
Barrigudo. 
Cai. 
Saki. 
N on-prehensile-tailed 
Squirrel Monkey. 
Douroucouli. 
Arctopithecini . 
. 
. Hapale .... 
Midas ..... 
Marmosets. 
Tamarins. 
The American Monkeys present some remarkable instances of the localisation and dispersion 
of species; allied kinds of different species, but with the same habits, occupying neighbouring 
districts, or being rather remote. And it is noticed that the great rivers form barriers between the 
homes of different kinds, which, however, mingle at the river source, and in the country not rendered 
impassable to them by broad streams. Thus Wallace noticed that the Howler ( Mycetes Beelzebub ) 
is apparently confined to the Lower Amazon, in the vicinity of Para, and a black species to the Upper 
Amazon, the Red Ursine Howler having the Rio Negro and the Upper Amazon as its forest ground. 
One Spider Monkey is found only in the Guiana district north of the Amazons, and another, the 
Ateles ater, inhabits West Brazil, but the speoies of the genus range, as a whole, over the forest 
regions from the south of Mexico to 30° south latitude, and even on the west of the Andes. 
The Lagothrix Monkeys, with their fine, furry coats, are found in the Ecuador district of the 
