In the TUKOTUKO (_Ctenomys brasiliensis_) and its congeners, about four of which are known from different parts of South America, one of them extending as far south as the Strait of Magellan, the eyes and ears are very small, and the animal seems to be still more specially adapted to a subterranean mode of life. In these animals the claws are longer than the toes, and those of the hind feet are fringed with a sort of comb formed of bristles. The incisor teeth are very broad. The Tukotuko is about the size of a large Rat, namely, from eight and a half to nine and a half inches long, with the tail from two and a half to three and a half inches. Its name is in imitation of the sound which it constantly emits--a sound which rather surprises a stranger when he first hears it, seeing that the animal uttering it is concealed underground. In many places, as in the Argentine Republic, this animal is exceedingly numerous, living generally in sandy soil, but sometimes in damp situations. It makes long burrows not far from the surface, and thus in some places completely undermines the ground. In making these galleries the Tukotuko is engaged in the search for its food, which consists chiefly of the roots of plants. According to Azara, it lays up stores of food in its burrows. Its activity is nocturnal. The CURURO (_Spalacopus Pöppigii_) has the ears quite rudimentary, and is also organised for a subterranean existence. This and another species inhabit Chili, where they make extensive burrows in the ground, and feed upon the bulbous and tuberous roots of various plants, large stores of which they collect in their subterranean abodes. These magazines are sought out by the poorer people, and their contents used as food. [Illustration: DENTITION OF THE ROCK RAT.] The ROCK RAT (_Petromys typicus_), although most nearly allied to the preceding species, lives on the opposite side of the Atlantic in the rocky hills of South Africa, especially towards the mouth of the Orange River. It differs from the preceding forms in the harshness of its fur, in which it resembles another sub-family of Octodontidæ, in the shortness of its thumbs, which are furnished with a small nail, and in its rather bushy tail. The molars are semi-rooted, with the enamel folds nearly meeting in the middle. The whiskers are of great length, and entirely black. The general colour is reddish-brown, with the head and fore parts greyish, the throat whitish, and the belly pale yellow. The tail is of the colour of the body at the root, with the remainder black. The length of the animal is about seven and a half inches, of the tail from five to five and a half inches. It feeds upon various vegetable substances, and appears to be very fond of the flowers of syngenesious plants, especially a species of groundsel, which it eagerly devours. It forms its retreat among loose stones, or in crevices of the rocks. [Illustration: TEETH OF THE SPINY RAT.]