124 MAMMALIA. 
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. 
Capromys, 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 a single one on the internal edge of the upper teeth, and the 
inverse in the lower ones. The tail is round and scantily philose; 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)*. Muzzle brown; the under part of 
the neck whitish; tail brown, but half the length of the body. 
Cap. prehensilis, Pessig.; Houtia Carvalli. Less than the pre- 
ceding; 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 Agoutis, at the time of the discovery, 
constituted the principal game of the inhabitants. 
Mus. Cuv. 
The Rats, properly so called, have three molars, of which the anterior 
is the largest; its crown is divided into blunt tubercles, which, by being 
worn, give it the shape of a disk, sloped in various directions; the tail is 
long and scaly. These animals are very injurious, from their fecundity, 
and the voracity with which they gnaw and devour substances of whatever 
kind. There are three species which have become quite common in our 
houses, viz. 
M. musculus, L.; Buff. VIL, xxxix. (The Common Mouse). 
Known in all times and at all places. 
M. rattus, L.; Buff. VII, xxxvi. (The Black Rat). Of which 
no mention is made by the ancients, and which appears to have en- 
tered Europe in the middle ages. It is more than double the size of 
the mouse, in all its dimensions. ‘The fur is blackish. Several in- 
dividuals have been occasionally found connected by the interlacing | 
of their tails; constituting what the Germans style the King of 
Rats.+ 
M. decumanus, Pall.; Buff. VIII, xxvii. (The Surmulot, or 
Common Norway or Brown Rat). Which did not pass into Europe 
till the eighteenth century, and is now more common in Paris and 
other large cities than the Black Rat itself. It is larger than the 
* This is the Isodon pilorides, Say. Zool. Journ. No. 2, p. 229. 
+ See Bellerman on the King of the Rats (in German), Berlin, 1820. 
