NORTH AUSTRALIAN MAMMALIA. 199 



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 bur- 

 rows 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 Murida, 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 com- 

 mencing to feed or retiring to rest. 



When thought to be unobserved this clumsy-looking animal 

 will exhibit surprising agility, and sometimes run with consider- 

 able swiftness. At the least danger it will immediately roll itself 



