142 MAMMALIA. 
Hypromys, Geoff. 
The Hydromys have many external points of relation to the Echi- 
mys, but they are distinguished from all other Rats by their hind 
feet, two-thirds of which are palmated; their two molars have also 
a peculiar character in the crown, which is divided into obliquely 
quadrangular lobes, whose summits are hollowed out like the bowl 
ofa spoon. They are aquatic. 
Several of these animals have been sent to Europe from Van 
Dieman’s land, some of which have the belly white, and others 
fawn coloured, but all of a deep brown above, with a long tail 
which is black at the base, and the posterior half white. They 
are sometimes double the size of the brown Rat. Hydromys 
leucogaster, and Hyd. chrysogaster, Geoff. An. Mus. VI, pl. 
XXXVI. 
Carromys, Desmar. 
The Houtias have four molars every where with flat crowns, the 
enamel of which is folded inwards so that it forms three angles on 
the external edge, and one only on the internal edge of the upper 
teeth, and the inverse in the lower ones. The tail is round and 
scantily pilose ; they have, like the Rats, five toes to the hind foot, 
and four, with the rudiment of a thumb, to the fore feet ; their form 
is that of a Rat; as large as a Rabbit or Hare. ‘Two species are 
known. 
Cap. fournieri, Desmar., Mem. de la Soc. d’Hist. Nat. de 
Par. I, 1823. (The Congo Houtia.)(1) Brown; muzzle and 
top of the neck whitish; tail brown, but half the length of the 
body. 
Cap. prehensilis, Poessig. Less than the preceding ; brown, 
with a whitish throat ; tail red, as long as the body, and partly 
naked.at the end. Both species inhabit the island of Cuba, and 
together with the @goutis, at the time of the discovery, consti- 
tuted the principal game of the Indians. 
Mus, Cuv. 
The true Rats have three molars every where, of which the ante- 
rior is the largest; its crown is divided into blunt tubercles, which 
by being worn, give it the shape of a disk, sloped in various direc- 
tions; the tail is long and scaly. These animals are very injurious 
from their fecundity, and the voracity with which they devour every 
(1) This is the Zsodon pilorides, Say, Zool. Journ, No. 2, p. 229. 
