belonging to the Order Rodentia. 123 
and though the imperfect nature of the materials at my disposal enables me 
rather to:excite than satisfy the curiosity which naturally attaches to the sub- 
ject, I may be permitted to indulge a hope that the present notice will at least 
attract the attention of future inquirers, and be the means of procuring more 
detailed and accurate information. 
That a vast majority of the terrestrial quadrupeds of Australia belong to 
the Marsupial family, a group in a great measure peculiar to that locality, 
and altogether anomalous in relation to the Mammals of other quarters of 
the globe, is a fact too well known to require further illustration. . At the 
same time, the exceptions to this general rule are much more numerous than 
has been hitherto suspected: it is true, indeed, that only five, or at most six 
species of Monadelphine quadrupeds have been hitherto described as indi- 
genous to that extensive continent; but the evidence which I shall produce 
in the present memoir gives us every reason to anticipate an extension of the 
number, whilst it establishes the singular and hitherto unlooked-for fact, that 
these exceptions belong exclusively to the Rodent order. Of the five or six 
monodelphine species already known to share this common habitat with the 
Marsupial family, one is the Dingo, or native dog, which, as I have observed 
above, should in all probability be expunged from the catalogue of aboriginal 
animals; three belong to the extensive and cosmopolite genus Mus; and the 
remaining one, or, perhaps, two species, constitute the genus Hydromys of 
M. Geoffroy St. Hilaire, the only nonmarsupial form hitherto described as 
peculiar to Australia. 
Under these circumstances, the announcement of any addition to the indi- 
genous Rodents of that country becomes in itself a matter of sufficient im- 
portance; but the discovery of new forms and genera, either altogether 
unknown, or hitherto unsuspected to exist in that quarter of the globe, in- 
vests the subject with more than ordinary interest, and whilst it enlarges the 
bounds of science, demonstrates the universality of those inscrutable laws 
which regulate the geographical distribution of animal life. It is, therefore, 
with feelings of more than common satisfaction that I present this memoir, 
however necessarily imperfect, to the notice of the Linnean Society ; more 
especially, as it affords me an opportunity of acknowledging my personal 
obligations to a gentleman to whom science and his country are equally in- 
R2 
