HYSTRICIDE 485 
(E. dorsatus), a stout heavily-built animal, with long hairs almost 
or quite hiding the spines; four anterior and five posterior toes ; 
and a short stumpy tail. It is a native of the greater part of 
Canada and the United States where there is any remnant of the 
original forest left. Remains of Hrethizon occur in cavern-deposits 
in Pennsylvania. 
Synetheres1—This genus contains some eight or ten species, 
known as Tree Porcupines (Fig. 214), found throughout the tropical 
ni 
WAN \\\ \ \ 
AY 
. WS Nyt 
WP 
Fic. 214.—The Tree Porcupine (Synetheres prehensitlis). 
parts of South America, and one of them extending northwards into 
Mexico. They are of a lighter build than the Ground Porcupines, 
are covered with short, close, many-coloured spines, often mixed with 
hairs, and their tails are always prehensile. Their hind feet have 
only four toes, owing to the suppression of the hallux; but they 
have a peculiar fleshy pad on the inner side of the foot, between 
which and the toes boughs and other objects can be firmly grasped 
as with ahand. Vertebre: C7,D17,L5,8 3, C 36. An extinct 
species of this genus has been described from the cavern-deposits of 
Brazil. 
1B. Cuvier, A/ém. du Muséum, vol. ix. p. 413 (1822). ‘‘ Sinéthére.” 
