Pectinator.[384]—Closely allied to the preceding, but with a minute premolar in each jaw; and a moderately long and bushy tail. One species (P. spekei), from Somali-land.

Subfamily Octodontinæ.—Molars semi-rooted or rootless, with simple enamel-folds; fur soft. There are some six existing genera, including Rat-like species, all of which are South American, except Petromys, which is Ethiopian.

Octodon.[385]—Upper and lower molars alike; ears moderate; tail of medium length and tufted. Vertebræ: C 7, D 12, L 7, S 4, C 25. Typically represented by C. cumingi of Chili and Peru, with other species from Chili and Bolivia. They live in large communities.

Habrocoma.[386]—Lower molars more complex than the upper; ears large; and fur extremely soft. Two Bolivian species.

Schizodon.[387]—One species, inhabiting elevated spots in the Southern Andes, and characterised by the enamel-folds of the upper molars meeting in the middle line. The external characters are much the same as in Ctenomys, but the ears are larger and the claws shorter.

Ctenomys.[388]—Incisors broad; molars rootless, with kidney-shaped crowns; last molar small and cylindrical; eyes and ears very small; claws larger than the toes. Some four species. Fossil remains are common in the Pleistocene of Buenos Ayres and the cavern-deposits of Brazil. Habits fossorial.

Spalacopus.[389]—Represented by two Chilian species, distinguished from the preceding genus by the rudimentary ears. These rodents store up magazines of food in their burrows.

Petromys.[390]—The South African P. typicus is closely allied to Spalacopus, but differs by its harsh fur, the shortness of the pollex, and the somewhat bushy tail. The teeth are semi-rooted, with single inner and outer enamel-folds, nearly meeting in the middle.

Subfamily Echinomyinæ.—Molars semi-rooted or rootless, with deep and curved enamel-folds; fur more or less harsh, frequently mixed with spines; tail generally long. One Ethiopian genus, and the remaining nine or so Neotropical. Many of the species are of large size, some being arboreal and others aquatic.

Myopotamus.[391]—Incisors very large; molars with two internal and two external enamel-folds in the upper, and three internal and one external in the lower jaw, last molar the largest; ears moderate; tail about two-thirds the length of the head and body, scaly, and sparsely haired; hind feet webbed; five digits. Vertebræ: C 7, D 13, L 6, S 4, C 25. The well-known Coypu (M. coypu), the only existing representative of this genus, is one of the largest living members of the order, and attains a length of about 2 feet. It is common in South America, living in burrows near water, and feeding on aquatic plants. Fossil remains of the genus occur in the caverns of Brazil, as well as in the Tertiaries of Argentina.

Capromys.[392]—This genus comprises arboreal forms from the West Indies allied to the Coypu, but, according to Dr. G. E. Dobson, showing signs of affinity with the Hystricidæ. The incisors are smaller than in the Coypu, and the upper molars have one internal and two external enamel-folds; the ears are comparatively small; the tail usually of considerable length, and the general form somewhat Rat-like. The typical C. pilorides is somewhat smaller than the Coypu, and is confined to Cuba; it is remarkable for the subdivision of the lobes of the liver into a number of lobules. C. brachyurus and C. prehensilis are also confined to Cuba. In Jamaica the genus is represented by C. melanurus, which is somewhat smaller than a Rabbit, and has no secondary lobulation of the liver.[393]

Aulacodus.[394]—Upper incisors with three deep grooves; molars as in Capromys. Fur very harsh; tail moderate, sparsely haired; manus with rudimentary pollex, and small fifth digit; pes with no hallux, and rudimental fifth digit. One species (A. swinderianus), from Western and Southern Africa, which attains a length of nearly 2 feet, and dwells in burrows.

Plagiodon.[395]—Allied to Capromys, but with the enamel-folds of the molars very complex, and forming a kind of zig-zag pattern in those of the upper jaw. Represented only by P. ædium of Hayti and Jamaica.

Loncheres[396] and Echinomys.[397]—These genera include small South American species, in most of which flattened lanceolate spikes are mingled with the fur. The majority of the species occur in Guiana and Brazil, but one species of Echinomys has been recorded from Central America. Fossil remains of both genera occur in the cavern-deposits of Brazil.

Mesomys.[398]—This genus resembles Loncheres externally, but the pollex has a short curved claw, and there are no spines in the fur.

Dactylomys.[399]—A Brazilian genus presenting the following distinctive features. Ears short; tail long and scaly; pollex minute; third and fourth digits of manus elongated, with short convex nails. Incisors flat; molars divided into two lobes, each of which has a single enamel-fold. Represented by two species, D. typus and D. amblyonyx, both of which seem to be rare and but little known. In the elongation of some of the digits Dactylomys recalls Chiromys among the Primates.

Cercomys.[400]—This South American genus is usually placed near Carterodon, from which it is readily distinguished by the pointed muzzle and the plain incisors.

Carterodon.[401]—This genus, which was originally described upon the evidence of skulls from the Brazil caves, but subsequently found living, is readily distinguished by the broad and grooved incisors. The upper molars have one inner and two outer enamel-folds; those of the lower jaw being the reverse of this.

Fossil Forms.—Remains of the existing genus Loncheres occur in the Brazilian cave-deposits, which also yield the extinct Dicolpomys. A large number of fossil Octodontidæ from the Tertiaries of South America have been described under many generic names, but it will be sufficient to mention that Phloramys and Pithanotomys are considered to be allied to Ctenomys; while Morenia, Orthomys, and Trilodon show affinity to Myopotamus. Pellegrinia, from the Pleistocene of Sicily, may be allied both to Ctenodactylus and Octodon.

Family Theridomyidæ.

This extinct family, which is represented in the Tertiaries of Europe and the United States, comprises several genera of comparatively small Rodents, which are regarded by Dr. Schlosser as nearly related to the Octodontidæ, although connected by Archæomys with the Chinchillidæ. The dental formula is the same as in the Octodontidæ. In the typical genus Theridomys, from the Lower Miocene and Upper Eocene of Europe, the molars are rooted, and have three or four re-entering enamel-folds, which form isolated discs on the worn crowns. Syllophodus, from the Miocene of the United States, is closely allied. Protechinomys and Trechomys are genera from the Phosphorites of Central France with rooted molars; while in Archæomys of the same deposits the molars are rootless, with the enamel-folds dividing their crowns into laminæ, as in the Chinchillas.

Family Hystricidæ.

Build stout. Limbs subequal. A number of long and stout spines in the integument. Facial portion of skull short and broad, and the jugal without an inferior angle. Molars with external and internal enamel-folds; completely or partly rooted.

Subfamily Synetherinæ.—Molars rooted; clavicles complete; upper lip not cleft; soles tuberculated; pollex absent; four mammæ; tail generally prehensile; spines mixed with long hairs. This group is confined to America, all the forms except one being arboreal, and their habits less strictly nocturnal than in the next subfamily. There are three genera.

Erethizon.[402]—Represented by the common Canadian Porcupine (E. dorsatus), a stout heavily-built animal, with long hairs almost or quite hiding the spines; four anterior and five posterior toes; and a short stumpy tail. It is a native of the greater part of Canada and the United States where there is any remnant of the original forest left. Remains of Erethizon occur in cavern-deposits in Pennsylvania.

Synetheres.[403]—This genus contains some eight or ten species, known as Tree Porcupines (Fig. 214), found throughout the tropical parts of South America, and one of them extending northwards into Mexico. They are of a lighter build than the Ground Porcupines, are covered with short, close, many-coloured spines, often mixed with hairs, and their tails are always prehensile. Their hind feet have only four toes, owing to the suppression of the hallux; but they have a peculiar fleshy pad on the inner side of the foot, between which and the toes boughs and other objects can be firmly grasped as with a hand. Vertebræ: C 7, D 17, L 5, S 3, C 36. An extinct species of this genus has been described from the cavern-deposits of Brazil.

Chætomys.[404]—Distinguished by the shape of its skull and the greater complexity of its teeth. It contains only one species (C. subspinosus), a native of the hottest parts of Brazil.

Subfamily Hystricinæ.—Molars semi-rooted; clavicles incomplete; soles smooth; a rudimentary pollex: six mammæ; tail not prehensile. Now confined to the Old World, where they occur in Southern Europe, Africa, India, and the Malay Archipelago as far eastwards as Borneo. Habits terrestrial and nocturnal. Three genera.

Hystrix.[405]—This genus is readily characterised by the inflated skull, in which the nasal chamber is often considerably larger than the brain-case, and by the short tail, tipped with numerous slender stalked open quills, which make a loud rattling noise when the animal moves. Vertebræ: C 7, D 15, L 4, S 4, C 12. The best-known member is the Common Porcupine (H. cristata, Fig. 215), which occurs throughout Southern Europe and North and West Africa, but is replaced in South Africa by H. africæ-australis, and in India by the Hairy-nosed Porcupine (H. leucura).

The following account of the habits of the last-named species is from Dr. Jerdon: “Hystrix leucura is found over a great part of India, from the lower ranges of the Himalayas to the extreme south, but does not occur in lower Bengal, where it is replaced by H. bengalensis. It forms extensive burrows, often in societies, in the sides of hills, banks of rivers and nullas, and very often in the dams of tanks, and in old mud walls, etc. In some parts of the country they are very destructive to various crops, potatoes, carrots, and other vegetables. They never issue forth till after dark, but now and then one will be found returning to his lair in daylight. Dogs take up the scent of the Porcupine very keenly, and on the Nilghiris I have killed many by the aid of dogs, tracking them to their dens. They charge backwards at their foes, erecting their spines at the same time, and dogs generally get seriously injured by their strong spines, which are sometimes driven deeply into the assailant. The Porcupine is not bad eating,—the meat, which is white, tasting something between pork and veal.”

Besides these three large crested species of Hystrix, there are four or five smaller species without nuchal crests occurring in North-East India and in the Malay region, from Nipal to Borneo.

Fossil species of Hystrix occur in the Pleistocene and Pliocene of India, and in Europe from the Upper Pliocene to the Middle Miocene, being perhaps also represented in the French Phosphorites. Remains from the Pliocene and Miocene of the United States have been referred to this genus, and if rightly determined are of especial interest from a distributional point of view.

Atherura.[406]—The Brush-tailed Porcupines are much smaller animals than the last, characterised by their long tails tipped with bundles of peculiar flattened spines. Of the three species two are found in the Malay region and one in West Africa. A fossil species occurs in the cavern-deposits of Madras.

Trichys.[407]—This genus contains but one Bornean species (T. guentheri), externally very like an Atherura, but differing from the members of that genus in many important cranial characters.

Family Chinchillidæ.

Terrestrial forms, with elongated hind limbs, bushy tails, very soft fur, and complete clavicles. Jugal without an inferior angle, and extending forwards to the lachrymal; palate contracted in front and deeply emarginate behind; incisors short, and the molars divided by continuous enamel-folds into transverse laminæ. Neotropical region. This family includes only three existing species, divided into as many genera.

Chinchilla.[408]—In this genus the fore feet have five and the hind four digits, the tail is long and bushy, and the auditory bullæ are enormous, appearing on the top of the skull. The one species (C. lanigera) is restricted to the alpine zones of the Andes from the north of Peru to the south of Chili. It is a Squirrel-like Rodent, about 10 inches in length, the tail somewhat exceeding 5 inches, and the ears very large. Its fur is greatly valued on account of its extreme softness and delicate gray colour.

Lagidium[409] and Lagostomus.[410]—Lagidium has four digits in both fore and hind feet, and Lagostomus three only in the hind feet, and the auditory bullæ are much smaller than in the preceding genus. Lagidium has the same distribution as Chinchilla; while Lagostomus, as represented by the Viscacha (L. trichodactylus), is found in the Pampas from the Uruguay River to the Rio Negro. The Viscachas live in burrows, generally in large numbers, and are nocturnal in their habits. Remains referable to the existing species, as well as others which appear to belong to extinct forms, occur in the Pleistocene deposits of South America.

Extinct Genera.—Several Rodents from the South American Tertiaries more or less closely allied to Lagostomus have been described by Dr. Ameghino under the names of Prolagostomus, Pliolagostomus, etc. The huge Megamys (Potamarchus), from the infra-Pampean deposits of Parana and Patagonia, is referred to this family, and has dimensions approximating to those of an Ox. Other fossil genera have received the names of Epiblema and Tetrastylus.

Family Castoroididæ.

Castoroides.[411]—The large Beaver-like Rodent with the dimensions of a Bear from the Pleistocene of the United States described under this name is regarded by Dr. Coues as the type of a family. Its dentition is nearest to that of Chinchilla and Hydrochœrus, but some of the cranial characters are like those of the Castoridæ. The genera Amblyrhiza and Loxomylus, from the Pleistocene of the Antilles, appear to be allied types.

Family Dasyproctidæ.

Terrestrial forms with subequal limbs, hoof-like claws, short or obsolete tail, and rudimentary clavicles. Mandibular masseteric ridge obsolete; palate broad; incisors long; molars semi-rooted, with external and internal enamel-folds. Neotropical region.

Dasyprocta.[412]—Includes several slender-limbed species, with three hind toes, commonly called Agoutis, inhabiting Central and South America, one (D. cristata) extending into the West-Indian Islands. Numerous fossil remains of this genus occur in the cavern-deposits of Brazil.

Cælogenys.[413]—This genus is readily characterised by the presence of five hind toes, and the extraordinary development of its zygomatic arches, which are enormously expanded vertically, forming great convex bony capsules on the sides of the face, enclosing on each side a large cavity lined with mucous membrane, and communicating by a small opening with the mouth. The Paca (C. paca) is about 2 feet long, and, like the species of Dasyprocta, lives generally in the forests or along the banks of rivers. This species appears to date from the epoch of the Pleistocene deposits of the Brazilian caves. A smaller species from Ecuador, living at elevations of from 6000 to 10,000 feet, has been described as C. taczanowskii.

Family Dinomyidæ.

Distinguished from the Dasyproctidæ by the cleft upper lip, rather long and bushy tail, the presence of four digits in both fore and hind feet, and the complete clavicles. The manubrium is broad; the optic foramina are confluent; the incisors broad; and the molars rootless, with enamel-folds dividing them into transverse laminæ.

Dinomys.[414]—The sole representative of this family is the Rodent known as D. branicki, of which hitherto only a single specimen has been obtained. This was captured in Peru, where it was found at daybreak walking about a courtyard; the inhabitants of the district were previously unacquainted with the species, from which its extreme rarity may be inferred. Externally it resembles much the Paca, having similar S-like nostrils; but in the laminated molars, and many features of the skeleton, it differs from all the other Rodents with hoof-like nails. It is regarded by its describer, the late Professor Peters, as a connecting link between the Octodontidæ, Chinchillidæ, Dasyproctidæ, and Caviidæ.

Family Caviidæ.

Terrestrial or natatorial forms, with short incisors, strong mandibular masseteric ridges, long and curved paroccipitals, and palate contracted in front. Fore feet with four digits, hind feet with three. Clavicles imperfect. Molars divided by enamel-folds into transverse laminæ; milk-teeth shed before birth. Other characters as in Dasyproctidæ. Neotropical region.

Cavia.[415]—Limbs and ears short, subequal; tail none. Vertebræ: C 7, D 13, L 6, S 4, C 7. This genus includes several species widely distributed throughout South America, extending even to the Straits of Magellan. The Restless Cavy (C. porcellus), which is found throughout Uruguay and Brazil, has been very generally regarded as the ancestral form of the domesticated Guinea-Pig. It is about 10 inches long, and weighs a little over a pound; its fur is long and of a nearly uniform grayish-brown colour. This species is rarely found in dry sandy localities, preferring marshes covered with aquatic plants, among which it lies concealed, feeding in the early morning and after sunset in the evening; but when the soil is dry it forms burrows. It lives in societies of from six to eighteen individuals, breeding but once a year, with one, or at most only two, young at a birth. The Guinea-Pig (probably a misnomer of Guiana-Pig) is larger than C. porcellus, and is regarded by Dr. Nehring as descended from another species, C. cutleri. It is white in colour, with irregular patches of reddish-brown and black. The Bolivian Cavy (C. boliviensis), found throughout the higher regions of Bolivia, usually at an elevation of 10,000 or 12,000 feet, is exceedingly shy, and lives in burrows, which in some districts are so numerous as to have completely undermined the soil. The Rock-Cavy (C. rupestris), distinguished by its short, blunt nails, is found in rocky situations throughout Brazil, and is much sought after for its flesh. The Southern Cavy (C. australis), common along the coast of Patagonia, forms deep burrows, with several outlets, in sandy declivities. Remains of existing species of Cavia are found in the cavern-deposits of Lagoa Santa, Brazil.

Dolichotis.[416]—Characterised by the great length of the ears and the short tail. The palate is so much contracted in front that the premolars of opposite sides touch by their antero-internal edges. Vertebræ: C 7, D 12, L 8, S 3, C 10.

The Patagonian Cavy (D. patachonica)—the only living representative of the genus—is rather larger than a Hare, which it somewhat resembles in external appearance. It inhabits the dry sterile districts of Patagonia and La Plata, disappearing wherever the country becomes more humid. This animal burrows in the earth, although in districts where the Viscacha is found it is said to avail itself of the works of the latter. Unlike other cavies, its eyes are protected from the glare of the sun by prominent eyelashes. The body is covered with a long dense fur of a rusty colour. Two young are produced at a birth. Three species of Dolichotis have been described from the Brazilian cave-deposits, one of which is probably not really separable from the existing form.

Hydrochœrus.[417]—A large aquatic form with all the feet fully webbed; the skull (Fig. 213, p. 481) large, with enormous paroccipital processes; and the molars very complex, the third upper one having some twelve transverse laminæ. Upper incisors grooved. Vertebræ: C 7, D 14, L 6, S 3, C 8.

The Capybara (H. capybara) is the largest existing Rodent, and the only living representative of the genus. It is a bulky and stoutly built animal, and attains a length of about 4 feet. The body is covered with long and coarse hair, reddish-brown above and brownish-yellow beneath. Capybaras are found over the whole of the eastern part of South America, and to the westward range into Bolivia and Peru. They frequent the borders of rivers and lakes, concealing themselves among reeds and other water plants. Remains of Hydrochœrus are found in the cavern-deposits of Brazil, which are probably referable to the existing species; one extinct species from the Pleistocene of Buenos Ayres is estimated to have attained a length of 5 feet, while H. magnus of the same deposits was of still larger dimensions. The genus is also represented in the Pleistocene of South Carolina and the infra-Pampean beds of Parana.

Extinct Genera.—A number of South American fossil Rodents have been referred to extinct genera of Caviidæ. Thus Plexochœrus, from the Tertiary of Argentina, differs from Hydrochœrus in having only nine laminæ in the last upper molar; Cardiomys, Cardiatherium, etc., from the infra-Pampeans are also stated to be allied to Hydrochœrus, while Contracavia, of the same deposits, is related to Cavia, but of larger size. Microcavia, again, from the Pleistocene of Argentina, is regarded as connecting Cavia with Dolichotis. The Tertiary European genera Issiodoromys and Nesocerodon are apparently referable to the present family.

Suborder Duplicidentata.

Two pairs of incisors in the upper jaw (the second very small, and placed directly behind the large first pair), the enamel of which extends round to their posterior surfaces. At birth there are three pairs of these incisors, but the outer one on each side is soon lost. Incisive foramina large; and usually confluent; bony palate very narrow from before backwards; no true alisphenoid canal; fibula ankylosed to the tibia, and articulating with the calcaneum. Testes permanently external. This suborder includes the Picas, Hares, and Rabbits, all of which are strictly terrestrial.

Family Lagomyidæ.

Complete clavicles, subequal limbs, no external tail, and short ears. Skull depressed, frontals contracted and without postorbital processes; p ¹⁄₁ or ²⁄₂; molars rootless, with transverse enamel-folds. Palæarctic and Nearctic.

Lagomys.[418]—Represented by about a dozen species of small Guinea-Pig-like animals, inhabiting chiefly the mountainous parts of Northern Asia (from 11,000 to 14,000 feet), one species only being known from South-East Europe, and another from the Rocky Mountains.

The Picas, or Tailless Hares, live in holes among the rocks of their native mountains, and are agile and shy little creatures. The genus is well represented through the upper and middle Tertiaries. It has been proposed to separate those fossil forms with p ²⁄₁ as Myolagus, and those with p ¹⁄₁ as Titanomys, but this seems scarcely advisable.

Family Leporidæ.

Imperfect clavicles, elongated hind limbs, short recurved tail, and long ears. Skull (Fig. 216) compressed, frontals with large wing-shaped postorbital processes p ³⁄₂; molars as in the Lagomyidæ. Cosmopolitan (except Australasia). Vertebræ: C 7, D 12, L 7, S 4, C 13-15.

Lepus.[419]—The single genus Lepus includes about twenty species, all of which resemble one another in general external characters. In all the fore limbs have five and the hind only four digits, and the soles of the feet are densely clothed with hairs similar to those covering the legs; the inner surface of the cheeks is also hairy. Although the family has such a wide distribution, the greater number of the species are restricted to the Palæarctic and Nearctic regions, only a single species (L. brasiliensis) extending into South America, where it has existed since the date of the Pleistocene deposits of the Brazilian caves.

The Common Hare (L. timidus[420]) may be taken as a typical example of the genus, and is characterised by the great length of the ears and hind limbs. It is found in all parts of Europe except the north of Russia, the Scandinavian peninsula, and Ireland. Its fur is usually of a tawny gray colour above and white beneath, with the upper surface of the short tail and the tips of the ears black. The colour of the fur differs, however, considerably in different latitudes and at different seasons of the year; showing a tendency to become white during winter in northern countries, while assuming a reddish-yellow hue in the more genial climate of southern Europe. The Hare is a nocturnal animal, remaining during the day on its “form,” as the slight depression is called which it makes in the open field, usually among grass.

The Mountain Hare (L. variabilis) is found throughout the northern part of the Palæarctic region, ranging from Ireland in the west to Japan in the east, and also occurring in several of the more southerly mountain ranges, such as the Pyrenees, the Alps, and the Caucasus. It is smaller than the common species, with a smaller and more rounded head, and shorter ears, tail, and hind limbs. In cold climates the colour of the whole animal changes in the winter to a pure white (as in Fig. 218), with the exception of the tips of the ears, which remain black. In Ireland no winter change of colour takes place.

The Rabbit (L. cuniculus), speaking of the wild race only, is distinguished from the Hare externally by its smaller size, shorter ears and feet, the absence or reduction of the black patch at the tip of the ears so characteristic of the Hare, and by its grayer colour. The skull is smaller and lighter, with a slenderer muzzle and a longer and narrower palate. Besides these characters, however, the Rabbit is sharply separated from the Hare by the fact that it brings forth its young naked, blind, and helpless; to compensate for this, it digs a deep burrow in the earth in which they are born and reared, while the young of the Hare are born fully clothed with fur, and able to take care of themselves in the “form” in which they are born. The weight of the Rabbit is from 2½ to 3 lbs., although individuals perfectly wild have been recorded up to more than 5 lbs. Its general habits are too well known to need a detailed description here. It breeds from four to eight times a year, bringing forth each time from three to eight young. Its period of gestation is about thirty days, and it begins to breed when six months old. It attains to an age of about seven or eight years.

The geographical distribution of the Rabbit presents many most interesting peculiarities. It is believed to be originally a native of the western half of the Mediterranean basin only, and still abounds in Spain, Sardinia, Southern Italy, Sicily, Greece, Tunis, and Algeria; and many of the Islands adjoining these countries are quite overrun with it. Thence it has spread, partly by man’s agency, northwards throughout temperate Western Europe, increasing rapidly wherever it gains a footing; and this extension is still going on, as is shown by the case of Scotland, in which sixty years ago Rabbits were little known, while they are now found in all suitable localities up to the extreme north. It has also gained admittance into Ireland, and now abounds there as much as in England. Out of Europe the same extension of range has been going on. In New Zealand and Australia Rabbits, introduced either for profit or sport, have increased to such an extent as to form one of the most serious pests that the farmers have to contend against, as the climate and soil seem to suit them perfectly, and their natural enemies are too few and too lowly organised to keep their numbers within reasonable bounds. In other cases Rabbits introduced into islands have become or remained more or less distinct from their parent stock; thus the Rabbits both of the Falkland Islands and of Jamaica still show traces of their descent from domesticated varieties, and have never reverted to the ordinary brownish-gray type. And again, as was pointed out by Mr. Darwin,[421] the Rabbits in the island of Porto Santo, near Madeira, whose ancestors were introduced from Spain in 1418 or 1419, have formed quite a distinct diminutive race, barely half the bulk or weight of English Rabbits, and differing in certain slight details of colour and habits.