460 7 ZOOLOGY. : : 
Loncheres, Isothrix, Mesomys, Echimys, Nelomys, and Aulacodon, belong’ to 
this section of hystricines. | 
Several fossil remains of this sub-family have been found in the caverns 
of Brazil, and which were described as species of Aulacodon, Nelomys, and 
Kchimys ; but the characters by which these genera are distinguished: being 
so difficult to trace out upon fragmentary remains, the genus Carterodon 
has been proposed, to unite them all. Besides, there is another species 
referred to the genus Loncheres, and still another to the genus Phyllomys, 
and a third, Lonchophorus, has been established. Its affinities. place it 
between Echimys and Loncheres, and it existed only during the period of 
the diluvium. ? 
Sub-fam. 5. Dasyproctina, are characterized among the other hystricines 
by semi-rooted molar teeth, arranged in parallel series. The feet are 
constructed for running, with five toes, or three only to the hind feet; 
terminated by sub-solid nails, which are but little arched. The tail is 
rudimentary; the body clothed with hair only, there being no admixture 
of spines. This sub-family includes two living genera. 
The genus Celogenys contains but one well established species, the 
Paca. ‘The zygomatic arch is very well developed and of great depth, the 
incisors slender, and five toes to the fore and hind feet. The Osteopera 
platycephala, of Harlan, is referred to this species. Fossil remains of one 
or more species of the present genus have been discovered in the Brazilian 
caverns. 
The genus Dasyprocta (aguti) has but three toes to the hind feet; the 
limbs are long and slender; the crown of the molar teeth rounded with a 
single fold of enamel, and four or five isolated grooves surrounded by 
enamel. The hinder parts of the back are covered with very long and 
coarse hairs. Several species of this genus are known in the actual fauna; 
the fossil remains of others are found in the Brazilian caverns. 
Sub-fam. 6. Hystricina proper, or porcupines, are provided with rooted 
or semi-rooted molar teeth; the feet are short, the number of toes variable, 
and the body more or less armed with spines. 
The porcupines are divided into two sections. One is composed of 
species living upon the ground and seeking shelter in burrows which they 
themselves form. They have five toes both to the fore and hind feet; the 
soles of the feet naked and smooth; the molar teeth semi-rooted and 
arranged in parallel series. The species of this section (Philogec) are 
confined to the old world. Those of the other section (Philodendre) are 
peculiar to the new world. They have climbing habits, and live almost 
entirely in trees. Their feet are usually provided with but four toes, and 
these are nearly equal in length, armed with long, compressed, and curved 
claws; sometimes, however, the hind feet have five toes. The soles of the 
feet are thickly studded with minute, depressed warts. 
The porecupines-of the new world, the Philodendre, are divided into 
three genera, Chetomys, Cercolabes, and FHrethizon. The first contains 
but one species, from Brazil; the second is more numerous, and is more 
widely spread. One of the species, C. villosus (pl. 118, fig. 3 a), inhabits 
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