252 Mr. R. I. Pocock on 
fingers are characters functionally correlated with the increased 
activity, and serve the purpose of giving at the same time 
a longer span and a safer grip on a branch when the animal 
alights from a long-distance spring. 
It might be held that the small hallux and the claw-tipped 
digits of the Hapalidze are primitive features derived direct 
from an unguiculate arboreal ancestor, probably of a lemuroid 
type, but preceding in those particulars modern lemurs, which 
have a hallux of great length and thickness and digits tipped 
with flat or flattish nails *. But, in my opinion, the Hapalide 
may be best regarded as derived from the typical Platyrrhine 
monkeys, from which they have departed in the numerical 
reduction of the teeth and in the appendicular particulars 
above-mentioned. The only Platyrrhine Primate outside the 
limits of the Hapalide which has the hallux small and the 
digits claw-tipped, as in the marmozets, is Callimico, Thos. ; 
and it is to be remembered that both in Callimico and the 
Hapalidee these characteristics of the hands and feet are 
associated with smallness in size and lightness in build. 
These little monkeys, indeed, are the most diminutive of all 
the true Primates, and, owing to the small size and narrow 
transverse span of the hands and feet, they are unable to 
grasp branches of any width. Nevertheless, since they are 
extraordinarily active and jump with great power, they require 
special means cf maintaining a hold on the branches they 
traverse or alight on. In this need may be found, I think, 
the modification of the nails into claws and the concomitant 
reduction of the hallux which, while depriving the hands and 
feet of the peculiar prehensile capacity seen in other Primates, 
have converted them into extremities resembling functionally 
those of squirrels in their power of hooking on to the rough- 
nesses of bark, of thick branches, and tree-trunks. 
The Ears.—In Hapale jacchus the ears are large, with the 
upper edge, which is folded, either evenly rounded or sub- 
angular posteriorly, and the posterior border, which is 
unfolded, also evenly and widely rounded and forming infe- 
riorly a continuously expanded lamina to a point just below 
the large fleshy valvular antitragus. The flap of the pinna 
extends widely beyond the central cavity of the ear both 
above, behind, and below, and its inferior portion just behind 
the antitragus shows a marked depression following the curve 
* With the exception, of course, of the second digit of the foot, which 
in every genus carries a claw, and also of all the digits, apart from the 
hallux, of Daubentonia (Chiromys), in which the nails have been con- 
verted into claws. 
