THE PACA. 289 
cated manner. They present in the very young state a 
somewhat different appearance from that which they 
assume in the full-grown animal, when their surfaces 
are worn down below the level of the tubercles by 
which they were originally surmounted. Generally 
speaking, they are marked by one or more foldings-in 
of the enamel on the inner side of the tooth, and by 
two or three transverse grooves surrounded by enamel, 
and not extending to the margin. These grooves are 
for the most part the remains of folds or tubercles which 
existed in the young state, and have been gradually 
effaced by the continued detrition of the surface; they 
consequently become less numerous and less strongly 
marked as the animal advances in age. 
Besides these peculiarities in their teeth, the Pacas 
are remarkable for having five toes to each of their feet, 
none of the other animals of the family having more 
than four on the fore feet and three on the hind, The 
thumb is, however, little more than rudimentary, and 
distinguishable merely by the presence of its claw. All 
the claws are broad, strong, and formed for digging in 
the earth. The Pacas are further distinguished by the 
total want of visible tail, there being only a slight pro- 
minence to mark the existence of that member; by 
the extreme shortness of their hairs, which are thinly 
spread and rigid to the touch; by their ears of mode- 
rate size, rounded at the tips, and forming several 
distinct folds; by their large open nostrils, occupying 
the extremity of a broad muzzle, which is separated 
into two portions by a vertical groove; and by the very 
great breadth of their faces. The last circumstance, 
which constitutes one of the most striking features of 
the group, is due to a singular conformation, the exist- 
ence of which was first pointed out by M. Geoffroy- 
Saint-Hilaire, in a specimen which died in the Paris 
l 
