RODENTIA. 139 
Keropon, Fred. Cuv. 
The Mocos have rather simpler grinders than the Cobayes, each being 
formed of two triangular prisms. 
The only species known is also from Brazil, somewhat surpasses 
the Guinea-Pig in size, and is of an olive-grey. 
Cutoromys, Fr. Cuv.—Dasyprocra, Iilig. 
The Agoutis have four toes before and three behind; four grinders 
throughout, almost equal, with flat crowns irregularly furrowed, rounded 
borders, notched on the internal edge in the upper jaw, and on the exter- 
nal one in the lower. In disposition, and in the nature of their flesh, 
they resemble Hares and Rabbits, which they may be said to replace in 
the Antilles and tropical portions of America. 
C. acuti ; Cavia acuti, L.; Buff. VIII. 1. 1, (The Common 
Agouti). The tail reduced to a simple tubercle; fur brown. The 
male fawn coloured on the croup; as large as a Hare. 
C. acuchi ; Cavia acuchi, Gm.; Buff. Supp. III. xxxvi. (The 
Acouchi). Six or seven vertebra in the tail; brown above, fawn 
coloured beneath; size of a Hare. 
C. patagonicus ; Cavia patagonica, Penn. and Schreb.; the 
Pampas Hare of the Creoles of Buenos Ayres. This animal 
appears to be a species of Agouti, with longer ears, and a very 
short naked tail; but its molars are not known. 
CaLogrenys, Fr. Cuv.* 
The Pacas, in addition to teeth very like those of the Agoutis, have a 
very small additional toe on the internal edge of the fore foot, and one on 
each side, equally small, on their hinder one, making five toes every 
where. Besides this, there is a cavity formed in their cheek which dips 
under the border formed by a very large and projecting zygomatic arch,} 
which gives a very extraordinary aspect to the bony head. Their flesh 
is said to be very good. 
There is one species or variety fawn coloured, and another brown, 
both of which are spotted with white, the Cavia paca, L.; Buff. X, 
xliii.; Supp, IIT. xxxv. 
Finally, there remains an animal perhaps nearly allied to the Cavias, 
and possibly more so to the Lagomys, or the Rats, which we are unable 
dispose of, on account of our ignorance of its teeth: this is the Chin- 
chilla, whose skins arrive in such abundance for furriers, but of which 
we have never yet been able to procure the entire body. It is the size of 
a Guinea-Pig or small Rabbit; is covered with long and close hair of the 
* Ancema, without strength; Chloromys, yellow rat; Dasyprocta, hairy buttock; 
Ceelogenys, hollow cheek; Hydrochcerus, water-pig. 
+ Dr. Harlan (Faun. Americ. p. 126) has made a new genus from a head pre- 
served in the Philadelphia Museum, which he names Osteopera; but, from the de- 
scription, it appears to us to be nothing more than that of the Paca. Desmarets has 
already made the same observation, 
