MAMMALIA. 



HVDROMVS, Geoffrey. 



The Hydromyt have many external points of relation to the Echimys, 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 of a spoon. They are aquatic. 



CAPROMYS, Desmarest. 



The Houtias have four molars every where with flat crowns, the enamd 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 feet, 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 : 

 one is the Cap. fournitri, Desmar. The other, 



Cap. prehentilis, Poessig. 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 Indians. 



Mus, Cuvier. 



The true Rats have three molars every where, of which the anterior is the 

 i 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 

 devour every thing that comes within their 

 reach. There are three species which have become quite common in our 

 houses, viz. 



M. miwrw/tw, Lin. (The Common Mouse.) Universally known. 

 M, rattus, Lin. (The Black Rat) Of which no mention is made by the 

 ancients, and which appears to have entered Europe in the tenth century. 

 It is more than double the size of the mouse in each of its dimensions. The 

 fur is blackish. Several individuals have been occasionally found connected 

 by the interlacing of their tails; constituting what the Germans style the King 

 of Pain. 



M. ilerumanus, Pall. (The Norway or Brown Rat) Which did not pass 

 into Europe till the eighteenth century, and is now more common in large 

 cities than the Black Rat itself. It is larger than the latter by one-fourth, and 

 differs from it also by its reddish-brown hair.* 



It appear* to belong to Persia, where it lives in burrows. It was not till 1727, that, 

 after an earthquake, it arrived at Astracan, by swimming across the Volga. 



