ORDERS OF MAMMALIA. 343 
bide, comprising the Spider-monkeys, the Howlers, and others. 
The Howlers (d/ycefes) are remarkable for having a bony 
drum at the summit of the windpipe, by which the voice is ren- 
dered extraordinarily resonant, and peculiarly weird and terrify- 
ing to those who hear it. 
Section C. Catarhina—In this, the highest section of the 
Quadrumana, the nostrils are oblique and placed close together, 
and the thumbs of all the feet are opposable, so that they are 
truly “quadrumanous.” The dental formula agrees with that 
of man : 
SoA = 2—2 
Z : = pm - ;m2 ‘=3 =o ter 
2—2 Slee 2—2 3—3 
The incisor teeth, however, are prominent and projecting, and 
the canines, especially in the males, are large and pointed, whilst 
the teeth form an uneven series. The tail is never prehensile, 
and is sometimes absent. Cheek-pouches are often present. 
In one single instance (Colobus) the thumbs of the fore-limbs 
are wanting. 
Fig. 187-—Quadrumana. Green Monkey (Cercocebus sabeus). (After Cuvier.) 
With the single exception of a Monkey which occurs on the 
Rock of Gibraltar, all the Catarhine Monkeys are confined to 
