qualities. It is a well-known fact that the termites to a great extent accomplish this work in tropical regions, and in Arnhem Land numerous ant-hills, sometimes of an enormous size, may be everywhere observed; but at the same time I cannot doubt that these small rodents perform a not unimportant part in this task of renewing the soil. The fact is that these rats are living in burrows deeply dug in the sandy ground, the earth being thrown out of the mouth of such retreats and spread outside in great heaps. However, they do not content themselves with this. Every night they continue burrowing, and the ground is perforated in all directions. In Arnhem Land I have travelled through square miles of country where the ground was literally undermined by these rodents to such an extent that the hoofs of my horses at nearly every step would break through and sink deep down in the burrows. The importance of this fact in the economy of nature can easily be understood. Every square mile of land in these localities is covered with heaps of sandy earth, sometimes dug out from a very considerable depth, and when the rainy season sets in and the ground is soaked the burrows collapse, the heaps are levelled, washed out over their surroundings, and the natural ploughing of the year is completed, while the little animals are compelled to recommence their task, and pay their house-rent by throwing earth up to the surface. Not only these Muridæ, but nearly every burrowing animal or reptile of this region decidedly perform a certain part—a small share—in the agricultural process of nature.
Echidna aculeata. "Melk"; "Guarang."
The Monotremes are in the north represented by a single form, the Echidna or "Porcupine" of the colonist. This species is found nearly all over the continent, and in Arnhem Land seemed to prefer the mountainous regions, especially the wildly broken granite and sandstone formations. In these localities it does not, as a rule, make use of its burrowing properties, but simply rests in some crevice or under the immense boulders, the setting and rising sun respectively being the signal for commencing to feed or retiring to rest.
When thought to be unobserved this clumsy-looking animal will exhibit surprising agility, and sometimes run with considerable swiftness. At the least danger it will immediately roll itself
