Golden-bellied and White-bellied Beaver Bat 
(HYDROMYS CHRYSOGASTER AND HYDROMYS LEUCOGASTER.) 
It is a strange fact that Beaver Rats have not yet been found beyond the Australian region, though they appear well 
adapted to lead an aquatic life, and seem able to cross the narrow straits dividing the mainland from New Guinea and 
the various groups of islands not strictly Australian. Whatever may be the cause, however, they do not inhabit other 
parts of the World, and are as peculiar to our Country as the Kangaroo. 
These rats have their grinders reduced to a pair in each ramus, above and below, and differ therefore from 
all other Rodents. It is difficult to determine how many species there are, and we believe that the four or five which 
naturalists choose to class as distinct, on account of a difference in fur, are in reality mere varieties of one kind. 
We have selected two well-marked species for representation, — the one bright orange, the other dirty white, 
beneath ; the upper parts are much alike, and of a grizzly brown or black colour. The tip of the tail is white in 
all species but one — Macleay’s Beaver Rat (Hydromys lutrilla). 
Trvo kinds are considered particularly doubtful, namely, the Fulvous Beaver Rat ( Hydromys fulvolavatm ), from 
the Murray River, and the Sooty Beaver Rat ( Hydromys fuliginosus) , from West Australia. The western animal is known 
to the aborigines of Perth as Ngoor-joo, whilst those who inhabit the country near King George’s Sound call it 
Ngoio" -ir-ri-gin. A third species was discovered by the late Mr. W. S. MacLeay, in front of his residence at Elizabeth 
Bay. This last rat has a uniformly dark tail, and is smaller than the others; but it is probably only an immature 
Hydromys leucogast.er. The original specimen in the Australian Museum has lost much of the fur, and its characteristics 
cannot be described with that certainty which is desirable when new species are under discussion. 
Beaver Rats are found in almost every part of Australia where there is permanent water; they become rare 
towards the tropics, and occur in large numbers in the southern streams and lagoons ; are shy and nocturnal in 
their habits ; dive well, but are soon drowned when unable to find a resting-place in the water. We have 
frequently tried the experiment in a large tank, and found them succumb in less than an hour. This fact may throw 
some light on the limited distribution of the genus. Their food consists of crustaceans, fish, and water insects, but 
principally of a small bivalve of the genus Cyclcis, which our talented artist, Mrs. Forde, informs us is to be found in 
the rivers of the interior in such large quantities that refuse-heaps of the empty shells always line the banks. The 
number of young is four at a Utter, and the mother provides a burrow' in the river-bank for them. The young ones 
are often feasted upon by snakes, and in one instance a dozen of them were taken from the stomach of a single reptile 
The bone caverns of this Country, w'hich have been most carefully examined, did not yield remains of these 
curious animals, though they have afforded proof that the Terrestrial and Arboreal Rodents lived in large numbers 
at a former age. It is not possible to add descriptions in this paper of the numerous rats and mice that inhabit 
Australia ; but w r e furnish a Ust of all the supposed species, w'hich may be found interesting. When more consideration 
is devoted by describing authors to teeth and structure of skeleton, and less to colour and texture of fur, these 
numerous species will suffer a heavy reduction, because one half of them are, no doubt, immature specimens, or local 
varieties. 
The dentition of the genus Hydromys is as follow's : — Incisors -, molars = 1 2 teeth. All other Australian 
rats and mice have- — -Incisors molars — , = 16 teeth. 
2 3-3 
The Rodents, Gnawers, or Rats, of Australia are conveniently divided into three groups, which we name — 1st, the 
genus Hydromys, comprising the water rats just enumerated; and, the genus Hapalotis , or the slender-eared and long-tailed 
rats; and, 3rd, the genus Mus, comprising the ordinary rats and mice. 
Genus Hapalotis. 
(a.) Tree Rats, representing the Squirrels in Australia; tail long, and generally pencilled at the tip: — 
1. White-footed Tree Rat. Hapalotis aibipes. New South Wales. 
1. White-tipped Tree Rat. Hapalotis apicalis. New South Wales. 
3. Black-tipped Tree Rat. Hapalotis penici/lata. North Australia. 
