CHAPTER III.

MOLE RATS, POUCHED RATS, POUCHED MICE, JERBOAS, AND OCTODONTIDÆ.

SPALACIDÆ, OR MOLE RATS--Characteristics of the Family--Habits--Food--THE MOLE RAT--Distribution--Description--THE CHESTNUT MOLE RAT--THE NAKED MOLE RAT--THE STRAND MOLE RAT--Description--Habits--THE CAPE MOLE RAT--GEOMYIDÆ, OR POUCHED RATS--Characteristics of the Family--The Cheek-pouches--THE COMMON POCKET GOPHER--Distribution--Description--Burrowing--Runs--Subterranean Dwelling--THE NORTHERN POCKET GOPHER--HETEROMYINÆ, OR POUCHED MICE--Difficulties as to Position--Characteristics--PHILLIPS’ POCKET MOUSE--Where Found--Description--THE YELLOW POCKET MOUSE--THE LEAST POCKET MOUSE--DIPODIDÆ, OR JERBOAS--Organisation for Jumping--Characteristics--Distribution--THE AMERICAN JUMPING MOUSE--Description--Characters peculiar to itself--Habits--THE TRUE JERBOAS--Characters--THE JERBOA--Distribution--Habits--Mode of Locomotion--THE ALACTAGA--THE CAPE JUMPING HARE--THE PORCUPINE-LIKE RODENTS--OCTODONTIDÆ--Characteristics--Sub-Family, CTENODACTYLINÆ--THE GUNDI--THE DEGU--Description--Habits--THE BROWN SCHIZODON--THE TUKOTUKO--THE CURURO--THE ROCK RAT--Sub-Family, ECHINOMYINÆ--THE COYPU--One of the Largest Rodents--Description--Burrows--Habits--Mother and Young--THE HUTIA CONGA--THE HUTIA CARABALI--THE GROUND RAT.

FAMILY VIII.--SPALACIDÆ (MOLE RATS).

Although the Zokor and its allies in the preceding family have to a certain extent prepared us for the peculiar characters presented by the Mole-rats, these are exhibited by the latter in a much more extreme form. They have a very large broad head, which is usually flattened above, and forms an appropriate anterior termination to a clumsy, cylindrical body, supported upon short stout limbs; their incisor teeth are large and broad, and are most formidably exposed in front of the mouth; their eyes are exceedingly small, hidden in the fur, and sometimes quite rudimentary; the external ears are reduced to the smallest possible size, or altogether wanting; and their tails are either so short as to be concealed within the hair of the hinder part of the body, or altogether wanting externally, although the skeleton still shows some caudal vertebræ. The molar teeth are rooted, and not tuberculate; their surface shows re-entering folds of enamel. The feet have five toes, but the thumb is generally very small, although furnished with a nail. The number of molars varies from three to six on each side in each jaw.

In their mode of life, as in their form and the condition of the organs of sight and hearing, these animals present a considerable resemblance to the Moles; but as their food is exclusively of a vegetable nature, the object of their burrowing is not exactly the same. They all inhabit the eastern hemisphere, and are generally met with in dry sandy plains, the soil of which lends itself readily to mining operations. They seldom quit their burrows, and usually work in these only at night, when they make their way rapidly through the ground, and, like the Mole, can run either backwards or forwards in their subterranean galleries with equal facility. They feed chiefly on roots, and especially on the bulbs and tubers which so many plants possess in the dry districts which they frequent; but some of them also eat nuts, seeds, the young bark of trees, and herbage. None of them fall into a state of torpidity during the winter--indeed, only two species inhabit northern regions; but these, although active in the winter season, are said not to take the precaution to lay up a store of provisions.

Most zoologists distinguish two groups of Spalacidæ. In the SPALACINÆ, the representatives of which range from south-eastern Europe to further India and the south of China, and also occur in Africa in the countries of Abyssinia and Shoa, the palate between the molar teeth is broader than one of the sockets of the molars, and the angular portion of the lower jaw springs from the lower edge of the bony case of the incisor. To this group belongs the MOLE-RAT (_Spalax typhlus_), which inhabits Hungary and Galicia, and the south-east of Europe generally, and ranges eastwards into Asia as far as the Caucasus and Ekaterinoslav. It possesses only three molars on each side in each jaw, and has the eyes rudimentary and covered by the skin, so that the animal is quite blind; the upper incisors are placed perpendicularly; and the tail reduced to a sort of wart. The toes, especially those of the fore-feet, are furnished with very powerful claws, which are vigorously employed by the animal in the digging operations above described. The general covering of the body is a soft fur of a yellowish-brown colour, tinged with ashy-grey; the head lighter, but becoming brownish behind; and the lower surface ashy-grey, with some white streaks and spots. The muzzle, chin, and feet are whitish, and along each side of the face there runs a sort of ridge of stiff bristle-like hairs. This species is particularly abundant in the Ukraine and the country about the Volga and the Don.

The genus _Rhizomys_, of which there are an East Indian and two African species known, has the eyes uncovered, though very small, short naked ears, and a short partially hairy tail. The upper incisors are arched forward. The CHESTNUT MOLE-RAT (_Rhizomys badius_) lives in Northern India, Siam, and Arracan; and, according to Mr. Finlayson, the food of a specimen in confinement consisted of unhusked rice and other grain, but he showed himself fond of yams and pumpkins. The NAKED MOLE-RAT (_Heterocephalus glaber_), which has no external ears and a short tail, has the body almost entirely naked. It is a native of Shoa.

The other section of the Mole rat family, the BATHYERGINÆ, is entirely confined to Africa, and, indeed, almost exclusively to the southern extremity of that continent, only a single species being found elsewhere--at Mozambique. They show a resemblance to the Hystricine Rodents in the structure of the lower jaw, the angular portion of which springs from the side of the bony case of the lower incisor; and the palate between the molars is narrower than in the Spalacinæ. The best known of the six species inhabiting the Cape of Good Hope is the STRAND MOLE-RAT (_Bathyergus maritimus_), which is nearly as large as a small Rabbit, its length being about ten inches, with a tail two inches in length. In general form it resembles the species last described; it has small but uncovered eyes, a broad nose, no external ears; very long, compressed, and powerful claws on all the toes, except the thumb of the fore-feet, which has a crooked nail; four molars on each side, and long white incisors, of which the upper ones are strongly grooved in front. The colour of the fur is greyish-white, with a yellowish tint on the upper surface. The tail has a sort of radiating tuft of hairs at the end. The Strand Mole-rat lives entirely in sandy localities near the sea-shore, and especially in the sand-hills or dunes which fringe the coast of the Cape of Good Hope in some parts. Here it burrows freely in all directions, its galleries generally radiating from several central points, and joining in various places. It avoids the light as much as possible, and if by chance it is exposed on the surface it is exceedingly helpless. Very little is known of the habits of this species, which probably feeds chiefly on roots like the other members of the family. It is regarded as mischievous, as it undermines the ground so much as to make it unsafe to ride over. The colonists, therefore, often destroy it by various means. The enamel folds of the teeth become effaced with use.

The _Georychi_, five species of which inhabit Cape Colony, resemble the preceding species, but are smaller and weaker. The claws of the fore-feet are shorter and weaker, and the upper incisors, which are long and arched forward, are not grooved. The best-known species is the so-called CAPE MOLE-RAT (_Georychus capensis_). In the Mozambique species (_Heliophobius argenteo-cinereus_) there are six molars on each side above and below, and the second toe of the hind feet is the longest. In most other characters it resembles _Georychus_.

FAMILY IX.--GEOMYIDÆ, OR POUCHED RATS.

The Pouched Rats, or Pocket Gophers, and the Pouched Mice of North America, constitute a family distinguished from all the preceding forms by the presence of a pair of great cheek-pouches, opening _outside_ and not inside the mouth (_see_ figure). These cheek-pouches are hairy inside throughout. The angular portion of the lower jaw is strongly twisted, the molars are four in number on each side in each jaw, and the squamosal bone is very large. In external characters the animals of this family present considerable diversity, which has led to their being divided into two well-marked sub-families, the distinctive peculiarities of which are of such importance that Dr. Coues has raised them to the rank of distinct families. The GEOMYINÆ, or Pouched Rats, are more or less Rat-like animals, in which the feet are five-toed, and all the toes furnished with claws, those of the fore feet being very strongly developed; and the tail is short. Certain other characters are presented by the skull. The outline of this part, including the zygomatic arches, is almost quadrangular; the infra-orbital opening is far in front of the jugal process; the malar bone extends forward to the lachrymal.

Of the animals thus characterised, the Continent of North America possesses, according to Dr. Coues, seven species, and they are met with from Hudson’s Bay and the Columbia River in the north, as far south as Mexico. The best-known species, the COMMON POCKET GOPHER (_Geomys bursarius_), inhabits the whole valley of the Mississippi, and extends northwards into Canada. It reaches the foot of the Rocky Mountains in Colorado, but is not known to occur west of that range. It is also found in Texas. This Pouched Rat, like the rest of its genus, has the incisors broad and the upper ones deeply grooved; but in addition to the ordinary deep groove it has a fine line close to the inner margin of each of these teeth. Its form is stout and clumsy, but its coat is beautifully soft and velvety, like that of the Mole, but of a dull reddish-brown colour, with the feet and tail white. The average length of an adult specimen is from seven to eight inches, and the tail is two or three inches long. This organ is clothed with hair nearly to the tip.

Like the Mole, this animal lives in burrows, which it makes in all directions in the ground, throwing out as it proceeds heaps of earth, which exactly resemble ordinary mole-hills. To enable it to perform these labours the claws of the fore feet are exceedingly powerful; and to adapt it the better to its subterranean existence, the eyes are very small, and the external ears are wanting. Its digging operations have generally the same object as those of the Mole--namely, the search for food. The tunnel is carried along not far from the surface of the ground, and the roots of any plants that lie in its course are bitten off and devoured by the little miner. Besides the runs, the Pouched Rat digs himself a convenient dwelling in the shape of a chamber hollowed out under the roots of a tree, access to which is gained by a somewhat spiral descending passage. This chamber, which is usually at a depth of four or five feet, is comfortably lined with soft grass, and the nest in which the female brings forth her young is a cavity of the same kind, but surrounded by circular passages, from which, like that of the Mole, other passages branch off. One of these, according to Gesner, leads from the nest to a large store-chamber filled with nuts, seeds, and roots, among which the potato was found to play an important part. These provisions are carried to the store-house in the great cheek-pouches, which the animal is said to fill by the aid of its tongue, and to empty with the fore paws. This Pouched Rat does much damage in cultivated ground by attacking the roots of both plants and trees, sometimes destroying a great number of the latter in a few days. The female produces from five to seven young at the end of March or the beginning of April. The other species of _Geomys_ closely resemble this in their habits.

Of the second genus belonging to this sub-family (_Thomomys_) Dr. Coues admits only two species, one of which, however, occurs under three named forms. They may be distinguished from the species of _Geomys_ by their having the upper incisors plain, without grooves.

The NORTHERN POCKET GOPHER (_Thomomys talpoides_), with its sub-species, ranges over nearly the whole of North America from the Hudson’s Bay Territory to California and New Mexico. The three forms are for the most part in accordance with geographical distribution. A small species (_Thomomys clusius_) has been obtained in the Rocky Mountains.

The HETEROMYINÆ (forming the family Saccomyidæ of Dr. Coues, although he does not accept the genus _Saccomys_) are more slender and delicate in form than the Geomyinæ, and have the hind limbs and tail elongated, the former, indeed, being converted into leaping organs like those of the Jerboas and Kangaroos. The eyes and ears are larger, and the animals are in every respect adapted to life in the open, while the Geomyinæ, on the contrary, are subterranean in their habits. The hair in the present family is coarse and harsh, sometimes even spiny. In skeletal characters we find a similar alteration. The incisors are narrow; the skull is delicate, with its angles rounded off, and the mastoid bones form a considerable part of the roof of the cranial cavity; the zygomatic arches are slender; and, the lower root of the maxillary process being undeveloped, the infra-orbital opening is not defined. As in the Jerboas, the cervical vertebræ are sometimes anchylosed. Like the Geomyinæ, these animals are confined to America, and chiefly limited to the Southern United States and Central America, although some of the species occur as far north as the Columbia River and Hudson’s Bay, and one is found in Trinidad. By American writers they are called “Pocket Mice.”

PHILLIPS’S POCKET MOUSE, also known as the Kangaroo Rat (_Dipodomys Phillipsii_), is one of the best known species of this group. It is an elegantly formed little creature, about four inches long, with a slender tail nearly six inches in length. Its colour above is mouse-brown, white beneath; the sides of the body have some white streaks, especially one from the ear towards the shoulder, and one on the thigh running towards the root of the tail; the tip of the tail is also white. This is a Californian species, but extends throughout the Pacific region of the United States. It is represented in the Rocky Mountains by a rather larger and stouter form, with smaller ears and a shorter tail (_Dipodomys Ordii_), which is generally regarded as distinct, but is placed by Dr. Coues as a sub-species. The habits of the species are comparatively little known, but they appear to live in the most desert places they can find, the barren spots on which the only plants that seem to flourish are the great mis-shapen cactuses. They dwell in holes under rocks and stones, from which they emerge at sunset, and hop about gaily after the fashion of little Kangaroos. The places in which these Pocket Mice are found are so bare of vegetation and destitute of water, that it is difficult to imagine how they contrive to exist. In all probability they pick up a scanty living in the shape of roots and grasses, especially seeds, carrying a supply for the day into their holes in their great cheek-pouches.

The YELLOW POCKET MOUSE and the LEAST POCKET MOUSE (_Cricetodipus flavus_ and _parvus_) are very minute creatures, only about two inches long in the head and body. The tail is longer than the head and body in the latter, shorter in the former species, and the colour of the fur in both is a pale buff. These species are found in the Rocky Mountains and the region west of that range to the Pacific, the latter being inhabited by the second of the above species. Several species of the genus _Heteromys_ inhabit Central America, and one is found in the island of Trinidad. Nothing appears to be known of their habits.

From these we pass as by a natural transition to

FAMILY X.--DIPODIDÆ (THE JERBOAS).

The JERBOAS are a more extensive and much more widely distributed family of hopping Rodents. In these we find the organisation for jumping brought to greater perfection than in any other group. The body is light and slender, the hind limbs much elongated, the fore limbs very small, and the tail long and usually tufted at the end. The number of toes on the hind feet varies from three to five, and the metatarsal bones are very often united so as to form what is called a “cannon bone” in the Horse. The incisor teeth are compressed; the molars sometimes four, but usually three in each series, rooted or rootless, not tuberculate; the infra-orbital opening is rounded and very large, and the zygomatic arch slender. The great home of these animals is the vast steppe region which stretches from South-eastern Europe across the greater part of Central Asia, but they extend southwards round the eastern extremity of the Mediterranean, through Syria and Arabia to Egypt and Africa, over a great part of which they are found, and eastward to India, Afghanistan, and Ceylon. A single species occurs at the Cape of Good Hope; and another is found in North America. We may commence by noticing this last species, as it not only makes the nearest approach to those of preceding families, especially the Muridæ, but differs from the rest of the Jerboas in characters of such importance, that Dr. Coues maintains its right to form a separate family (_Zapodidæ_).

The AMERICAN JUMPING MOUSE (_Zapus[54] hudsonius_) has a wide range, extending across the continent of North America from sea to sea, and from Labrador, Hudson’s Bay, and the Great Slave Lake in the north, to Virginia and the elevated portions of Arizona and New Mexico in the south. It is an elegant little mouse-like creature, rather more than three inches long, and furnished with a cylindrical tail, which exceeds the head and body in length by about two inches. Its hind limbs are not quite so disproportionately developed as in the other members of the family. Its fur in summer is of a brown colour above, becoming yellowish on the sides and white below; in the winter the brown tint covers the whole surface. The ears, which are not very large, are black, with a light-coloured rim; the hind feet are greyish, and the fore feet whitish on the upper surface; and the tail, which tapers to an exceedingly fine point, where there is a fine pencil of hairs, is ringed and nearly naked.

The characters in which this animal differs from its nearest relatives are as follows:--In the upper jaw there are four rooted molars on each side, the first being very small, the second the largest, and the rest gradually diminishing in size; the fore feet have the thumbs rudimentary, and the hind feet have five toes, all of which touch the ground; the metatarsal bones are separate; and the soles of the feet naked, with granules and small horny shields.

The American Jumping Mouse is found in meadows in the neighbourhood of woods and copses. It is nocturnal in its activity, sleeping during the day in its burrow, which is usually about two feet deep, and coming forth at night. It is sociable in its habits, and excessively active, covering from three to five feet of ground at each leap, so that it is a matter of no little difficulty to capture a specimen in the open. In the woods it is worse, as the little creature will bound over bushes, and get out of sight in a moment. Its food consists of seeds of various kinds, and it is exceedingly fond of beech-mast. For protection from the cold of winter the Jumping Mouse makes a little hollow clay ball, within which it coils itself up, and goes comfortably to sleep. The nest is made about six inches under the surface of the ground, and is composed of fine grass, sometimes mixed with feathers, wool, and hair; and in this the female produces from two to four young, probably several times in the course of the summer, as the nests and young are to be found from May to August.

If we regard the American Jumping Mouse as constituting a peculiar section of the family, ZAPODINÆ, a second group, DIPODINÆ, is formed by the TRUE JERBOAS, which make up the greater part of the family. These either possess only three molars, or a very small additional tooth exists in front of each series in the upper jaw. The molars are rooted, and diminish in size backwards in each series. The cervical vertebræ are anchylosed; the fore feet have the thumbs rudimentary, but sometimes furnished with a small nail; the hind feet have only three toes fully developed, and the metatarsals are united into a single bone of great length; the soles are furnished with elastic balls; and the tail is very long, well-clothed with hair, and tufted at the end.

Of these pretty little creatures, which are in some respects singularly bird-like, about twenty species have been recorded, and these occupy the whole of the Old World area of the family, except South Africa. The JERBOA (_Dipus ægyptius_) may serve as an example of this section of the family. This is a most lively and active little creature, which inhabits the deserts of north-eastern Africa as far south as Nubia, and extends its range into Arabia and south-western Asia. On these arid plains, so scantily clothed with a few grasses and dry shrubs that it is difficult to conceive how any animal can find a living on them, the Jerboa lives, often in numerous societies, and in company with the few birds and lizards which enliven the wilderness. These animals dwell in subterranean abodes consisting of many branched galleries, which they dig out in the hard soil not far from the surface. The Arabs assert that these habitations are produced by the joint labour of the whole society. They retreat into their burrows at the least alarm. The females are said to produce from two to four young at a birth in a nest made in the deeper part of the burrow, and lined with hair pulled from the under surface of her own body. When going along quietly, the Jerboa walks and runs by alternate steps of the hind feet, but when there is occasion for rapid motion it springs from both feet at the same time, covering so much ground at each leap, and touching the ground so momentarily between them, that its motion is more like that of a bird skimming close to the surface of the ground than that of a four-footed beast.

The Jerboa is about six inches long, with a tail about eight inches in length exclusive of the tuft with which its tip is adorned. Its upper surface is of a greyish sand-colour, like that of many other desert animals; the lower surface is white; and the tail pale-yellowish above and white beneath, with the tuft white, with an arrow-shaped black mark on its upper surface.

Several other species of Jerboas are known, some from the deserts of North Africa, others from the steppes of Central Asia. The latter region harbours some forms, which differ from the preceding, among other characters, by having five toes in the hind feet, whereas the true Jerboas have only three, but of the five toes only three are sufficiently developed to take part in the animal’s progression. The best known of them is the ALACTAGA (_Alactaga jaculus_), a rather larger species than the Jerboa, and with a still longer tail, reddish-yellow with a greyish tinge above, white beneath and on the hind legs. Its range extends from the Crimea and the steppes of the Don across Central Asia to the borders of China. It walks upon all-fours, and when advancing quickly springs along after the fashion of the Jerboa. Its food consists of all sorts of vegetable substances, but it is especially fond of the bulbs of plants, and does not refuse occasionally to eat insects, or even the eggs and young of the birds which inhabit the steppes with it. The Alactagas live in very complicated burrows, with many passages and branches, and they are said always to make one passage from the central chamber of their residence, which terminates close to the surface of the earth at some distance, but is only opened in case of danger, when the inhabitants escape through it, the position of its intended aperture being previously unrecognisable. In cold weather they sleep in their nests. The female produces from five or six to eight young, in a nest lined with her own hair. Species of _Alactaga_ occur not only in Central Asia, but also in Arabia and North Africa.

South Africa produces one species, the CAPE JUMPING HARE (_Pedetes caffer_), which constitutes a distinct sub-family, PEDETINÆ, having four rootless molars on each side in each jaw, the metatarsal bones separate, the tail bushy, and the hind feet furnished with four toes having broad, hoof-like nails. This is a much larger animal than any of the preceding, being about the size of the common Hare, which it also resembles in its colours. The Jumping Hare inhabits a considerable portion of South Africa, extending on the west coast at least as far as Angola. It is abundant at the Cape of Good Hope, both in the mountains and in the plains. Great numbers of the animals often live together, and their burrows, which, like those of other Dipodidæ, are inhabited by numerous individuals as a common residence, consist of many-branched galleries made at no great depth from the surface, but leading into a more deeply-seated habitation. They generally go about slowly upon all-fours, but can advance with extraordinary rapidity by Kangaroo-like springs, in each of which, when pressed, they will cover a space of twenty or thirty feet. Their food consists of roots, seeds, and herbage. The female produces three or four young at a birth.

SECTION III.--PORCUPINE-LIKE RODENTS (_HYSTRICOMORPHA_).

FAMILY XI.--OCTODONTIDÆ.

This first family of the Porcupine alliance consists of a number of rat-like animals, nearly all of which are inhabitants of South America, three species only being peculiar to the large West Indian Islands, whilst, singularly enough, four more are known from different parts of the African continent. Except in one of these last, all the members of the family have four molars on each side in each jaw, and the crowns of these teeth show internal and external folds of enamel. The malar portion of the zygomatic arch has an angular process at its lower margin. The hind limbs are not disproportionately developed, and both they and the fore feet are nearly always furnished with five toes, armed with curved claws; and the clavicles are perfect. The ears are generally short and sparingly hairy, and the tail, which is of various lengths, is either clad with short hairs, or naked and scaly.

We may begin with two African species of this generally American family, which have the two inner claws of the hind feet furnished with comb-like fringes of horny bristles, whence the name of _Ctenodactylus_ has been applied to the best known species. These two species, which exhibit strong affinities to the Jerboas, form the sub-family CTENODACTYLINÆ. The GUNDI (_Ctenodactylus Massoni_) has only three molars on each side in each jaw, and only four toes upon each foot. It is an animal about the size of the Water Rat, but with a mere stump of a tail, very small ears, very long whiskers, and the hind limbs rather longer than their fellows. It lives in North Africa, chiefly on the borders of the Sahara, where it takes up its abode in the rocky hills, and descends therefrom to the cultivated grounds to feast upon the growing corn. It is diurnal in its habits, but exceedingly shy and watchful, making off to its fastnesses at the least appearance of danger. _Pectinator Spekei_, a species named after its discoverer, the celebrated African traveller, is nearly related to the preceding, but has a small additional molar in each series. The tail is of moderate length, and bushy, and the ears have a small antitragus. It inhabits the Somali land in the interior of North-eastern Africa.

The DEGU (_Octodon Cumingii_), a very abundant species in Chili, which also extends into Peru, may be taken as a typical example of the whole family, and also of its typical sub-family OCTODONTINÆ, in which the molars are simply indented on each side. The fur is soft, and the tail is short. The Degu is a rat-like animal, rather smaller than the Water Vole, the head and body measuring from seven and a half to eight inches in length, and the tail, exclusive of its terminal tuft, rather more than half that length. The general colour of the animal is brownish-yellow, pencilled with black on the back; the lower surface is yellowish, the feet white, and the tail dusky above, whitish beneath, with the tufted tip dusky or blackish. In the central parts of Chili, according to various travellers, the Degu is exceedingly abundant, living in large societies about hedges and thickets, and running about boldly, even on the high roads. The animals make their burrows in the hedge-banks and similar places, and when alarmed rush into them with their tails elevated, very much after the manner of Rabbits. As the burrows communicate freely with each other, the Degus can easily escape pursuit, going in at one opening and coming out at another at some considerable distance. They sometimes climb up into the bushes among which they live. Their ordinary food consists of the herbage which grows about their dwelling-places, but they also invade gardens and fields, where they may do considerable damage. In the winter they will feed upon the tender bark of certain trees, but they are said by some authors to lay up a store of food against this season. They do not become torpid. The female is believed to produce two broods in the year, each consisting of from four to six young. Two other species of _Octodon_ are known from Chili and Bolivia, which region is also inhabited by two species of _Habrocoma_, a genus distinguished by the large size of the ears, and the extreme softness of the fur. In these animals the molar teeth differ in the two jaws, the upper ones being as simple as in the preceding species, while the lower ones show a complication of the enamel folds like what we shall meet with in the third sub-family.

The BROWN SCHIZODON (_Schizodon fuscus_), which inhabits certain elevated spots in the southern part of the Andes (75° S. lat.), has the enamel folds of the molar teeth meeting in the middle. It is about the size of the common Rat (seven and a half to nine inches long), and has a shortish tail clothed throughout with short hairs. Its fur is dark brown above, dirty yellowish beneath. This animal inhabits grassy places near mountain streams, where the ground is sometimes so undermined by its burrows as to render travelling on horseback very uncomfortable. It is a nocturnal animal, and passes most of its life underground. The valleys it inhabits are covered with snow for at least four months in the year.

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.

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.

While the Octodontinæ may be regarded as specially characteristic of the region of the Andes, the other great group of this family is almost exclusively confined to the country east of that great chain, and to some of the West Indian islands. Curiously enough this sub-family also has a single representative in Africa. Its members are distinguished at once by the complicated enamel folds of their molar teeth in both jaws, by these teeth being generally rooted, and by the texture of the fur, which is harsh and frequently mixed with fine spines. Hence the name of _Echinomys_ (Spiny, or rather Hedgehog, Rat), applied to the typical genus, from which the sub-family is named ECHINOMYINÆ. The tail in these animals is usually long.

The Rodents belonging to this sub-family are generally of considerable size, as large as Rats, or larger, stoutly built, with the hinder part of the body larger than the fore-quarters, with limbs of moderate length, the hinder larger than the anterior, the former furnished with five toes, the latter with four complete digits and a rudimentary thumb, and the toes armed with strong curved claws. The tail is scaly, with scattered hairs. In their habits these animals appear to be strictly vegetable-feeders, but in other respects they present some variety. The majority live in and upon the ground; but one or two are arboreal, and one aquatic, in their mode of life.

The last species alluded to is the well-known COYPU (_Myopotamus Coypus_), one of the largest of Rodents, which occurs in nearly all parts of South America and on both sides of the Andes, from the tropic of Capricorn to about 15° N. lat. It is usually about twenty inches long, but often attains still greater dimensions. The tail, which is about two-thirds the length of the head and body, is scaly, with hairs about as thickly scattered as in the common Rat. The ears are of moderate size; the incisor teeth very large and powerful; the molars, the hindmost of which are the largest, have two internal and two external enamel-folds in the upper, and three internal folds and one external in the lower, jaw; the hind feet are webbed. The general colour of the upper surface is brown, produced by dusky and brownish-yellow pencilling; the sides and under parts are brownish-yellow, and the front of the muzzle and the chin white.

The Coypus live upon the shores of the rivers and lakes of South America, generally, according to Rengger, in pairs, each pair digging for themselves a burrow in the bank, which extends to a depth of three or four feet, and widens out into a cavity eighteen inches or two feet in diameter. Here they pass the night, and take refuge when necessary during the day. They select for their dwelling-places the stiller parts of the water, where the aquatic plants on which they chiefly feed grow freely. They are said to swim well, but not to be expert in diving. On land they are slow and awkward in their movements. They feed chiefly on the roots of plants, but in the Chonos Archipelago, where the Coypus frequent the sea and make their burrows at some little distance from the beach, they are said occasionally to eat shell-fish. The female produces from four to five young once in the year. The little animals very early accompany their mother into the water, when she swims with them on her back, until they have acquired the art of swimming. Mr. Waterhouse thinks that this habit may “explain the singular position of the nipples noticed in the female Coypu. Of these four were found by Mr. Lereboullet on each side of the body, and situated rather above the mesial line of the flanks, the foremost being placed behind the shoulder, and the hindermost in front of the thigh.” The Coypu is hunted for the sake of its flesh, which is described as white and of good flavour, and of its skin, which is well known in the fur trade under the name of “Nutria,” signifying Otter. Great quantities of these skins are annually exported from Buenos Ayres. It is said to be a courageous animal, fighting bravely with the dogs engaged in chasing it.

The HUTIA CONGA (_Capromys pilorides_) is another large Rodent, measuring from twenty to twenty-two inches in length, with a stout rat-like tail about half as long as the head and body. It is an inhabitant of Cuba. The incisors are considerably smaller and weaker than in the Coypu; the upper molars have one internal and two external folds; the lower ones are similar but reversed. The fur, which is long, is very harsh, and consists of a mixture of black and yellow hairs, becoming rusty on the hinder part of the body. The belly is rusty yellow. This animal lives in the dense forests of Cuba, where it resides either upon the trees or in the thick underwood. It is a nocturnal or crepuscular animal, and is tolerably active when going about on the branches of trees, but is less at home on the ground. Its food consists of fruits, leaves, and the bark of trees, but, according to M. Ramon de la Sagra, it does not disdain animal food, and is especially fond of a species of Lizard belonging to the genus _Anolis_. On the other hand, the negroes are very partial to the flesh of the Hutia, and they capture the animal either by snaring it on the branches of trees, or by sending Dogs after it. Like the Coypu, it is said to fight courageously against its pursuers. Another Cuban species, the HUTIA CARABALI (_C. prehensilis_), has a slightly longer tail, which is prehensile at the tip. It is described as keeping chiefly to the highest branches of the trees. In St. Domingo there is an allied form, _Plagiodon ædium_, in which the enamel folds of the molars are singularly complex (_see_ figure on p. 132). This animal frequents the neighbourhood of human habitations, and approaches them at night in search of its food, which consists of fruit and roots. In most of the other members of this sub-family, which appear to be terrestrial in their habits, the intermixture of spines with the fur of the back is a striking character. In the genus _Echinomys_ itself, and in _Loncheres_, which together include about a dozen species found chiefly in Guiana and Brazil, the spines frequently form the principal outer covering of the back. Side by side with these hedgehog-like species, however, others occur in which the fur is soft.

The GROUND RAT (_Aulacodus Swinderianus_), of Western and Southern Africa, is remarkable as being the sole representative of this group outside the South American province. It has very broad incisors, and those of the upper jaw exhibit three deep grooves; the molars show the same arrangement of folds as in _Capromys_; the fur is harsh and bristly, and of a general brown tint; and the tail is of moderate length, sparingly haired, dusky above, and whitish below. The fore feet have the thumb rudimentary and the outer toe very short; and the hind feet have only four toes, of which the outer one is rudimentary. This curious animal, which is nearly two feet long, is known to be an inhabitant of Sierra Leone and the Gambia, and also of South Africa (Port Natal); in all probability it occurs at many intermediate localities. In Sierra Leone it is known as the Ground Rat, or Ground Pig, and is said to feed upon ground nuts, and cassada and other roots in search of which it digs into the ground, where it also forms large burrows for its residence.