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Zoological Society. 55 
eminent zoologists as a species of Cebus which had lost part of its tail ; 
but there was a peculiarity in the position of the thumb as regarded 
the fingers, which at once showed that whatever might be the natural 
length of its tail, it evidently did not belong to the genus Cebis as at 
present restricted. The examination of the animal after death showed 
that it was a most distinct genus, and nearly related to, ifnot a variety 
of, Brachyurus Ouckari of Spix. 
I may observe that the genus Brachyurus was established by Spix 
in his work on American Monkeys for two species, viz. 1. the Szmia 
Chiropotes of Humboldt (the 8. Sagulata of Trail), which has been 
generally referred to the genus Pithecia ; and 2. Brachyurus Ouakari. 
Spix in the same work restricted the genus Pithecta to the Saki or 
Long-haired American Monkeys. 
The examination and comparison of the skuli of the short-tailed 
monkey and of the allied genera have induced me to think that the 
American Monkeys with long hairy tails, and with six grinders, may 
be divided into two very natural subfamilies, characterized by the 
position and form of the cutting teeth. 
The first of these groups I should propose to call Callitrichina : 
they have small erect cutting teeth, forming a regular series with the 
canines. This group contains the genera Callithrix and Chrysothriz, 
with small diurnal eyes, and Nyctipithecus, with large nocturnal eyes. 
The second group, which may be called Pitheciana, have the cutting 
teeth large, converging together, and separated from the canines by 
a large space, and their under ones more or less shelving. This group 
contains three genera, viz. :— 
1. Pithecia. The fur elongate, dry, harsh; the tail club-shaped ; 
the crown like a wig, and the chin slightly bearded ; the lower cutting 
teeth rather shelving. 
This is the genus Pithecia, as restricted by Spix, the Yarkea ot 
Lesson, containing P. monachus, P. leucocephalus, and P. rufiventei 
of Geoffroy. 
Spix (tab. 37. f. 4) figured a skull which appears to belong to a 
species of this genus, but he does not indicate its name. 
2. Brachyurus. The fur silky, short; tail elongate club-shaped ; 
the crown like a wig, and the chin largely bearded on each side; the 
lower cutting teeth are rather shelving ; limb short and straight. Con- 
taining Cebus satanas of Hoffmanseg, which is the type of Spix’s 
genus. 
Lesson has given the name of Chiropotes to this group, and Cucajao 
to a second group, established on the Sima melanocephalus of Hum- 
boldt, which is probably only a badly stuffed specimen of this species. 
Spix, in his work on Brazilian Monkeys, figures a skull which ap- 
pears to belong to this genus, but it is like several others on the same 
plate, without any name, t. 37. f. 5. 
3. Ouakaria. The fur short, silky ; tail short, subcylindrical, the 
crown with short hair; the chin scarcely bearded ; the lower cutting 
teeth very much shelving ; legs elongate. 
This genus forms part of the genus Brachyurus of Spix; and if 
Spix had not evidently described the teeth, &c. of his first species in 
