Commencing with the most lowly organized of the Australian mammals, I may state that the Ornithorhynchus has a very limited range, as is shown by its not being found either in Western or Northern Australia—the south-eastern portions of the continent and Van Diemen's Land being the localities to which it is confined.
The spiny Echidna hystrix has not yet been found to the northward of Moreton Bay on the east coast, and, except in New South Wales and the islands in Bass's Straits, it is very rare—so rare indeed, that I have never seen a specimen from South Australia; yet in all probability it will be found there, since Mr. Gilbert obtained an example at Swan River; this individual, however, did not come under my notice, and I am therefore unable to say if it were a true E. hystrix, or a western representative of that species.
The more hairy Echidna setosa is confined to Van Diemen's Land; but it is questionable whether it be really distinct from E. hystrix; the more southern position and colder climate of that island may have had the effect of giving it a warmer coat, whiter spines, and of altering its general appearance.
The single species representing the genus Myrmecobius (M. fasciatus) appears to be more plentiful in the Swan River Settlement than elsewhere; it nevertheless occurs in the Murray Scrub and other parts of South Australia, and from thence to the western coast it probably inhabits every locality suited to its habits and mode of life.
Like the Myrmecobius, the little honey-lapping Tarsipes rostratus stands quite alone—and a truly singular creature it is: to give the area over which it ranges is impossible, as we know far too little of these diminutive mammals to come to any positive conclusion on this point; at present, the neighbourhood of King George's Sound is one of the localities in which it has been seen in a state of nature.
Isolated in form and differing in the structure of its feet from every other known quadruped is the Chæropus, an animal which
