Chœropotamidæ.—In this family the molars are intermediate in structure between those of the Suidæ and the next family. The upper ones have very broad crowns, with the five columns arranged as in Anthracotherium; while the premolars are not secant, and may be very large. The best known forms are the small Cebochœrus of the Phosphorites of Central France; Chœropotamus of the Upper Eocene, the type species of which was of the size of a large Pig, with the dental formula i ³⁄₃, c ¹⁄₁, p ⁴⁄₃, m ³⁄₃, and no distinctly selenodont structure in the molars; the much larger Elotherium, from the Upper Eocene and Lower Miocene of both the Old and New Worlds, which presents the very rare feature of the absence of a third lobe to the last lower molar; and the equally large Tetraconodon of the Pliocene of India, in which this third lobe was present and the premolars were of enormous size. The remarkable North American Eocene genus Achænodon should perhaps also be placed here.

Anthracotheriidæ.—The genera Anthracotherium and Hyopotamus, of the upper Eocene and Miocene, have the typical Eutherian dental formula; the upper molars (Fig. 111) carrying three columns on the anterior and two on the posterior half of the crown, all of which are of a more or less decidedly selenodont structure. The mandible has a descending flange at the angle. The figured tooth (in which the antero-internal and antero-median columns are imperfect) may be compared with the diagram given in Fig. 5, p. 32, when the homology of the columns or tubercles will be at once apparent, the broken antero-median column representing the protoconule. Some of the species are of large size, while others are comparatively small.

Merycopotamus.—The genus Merycopotamus of the lower Pliocene of India may be regarded as an Anthracotheroid which has lost the antero-median column to the upper molars (Fig. 112), so that these teeth are consequently quadrituberculate; and may thus be regarded as typical examples of the brachy-selenodont modification of molar structure.

Cotylopidæ.—The Miocene genus Cotylops (Oreodon[185]) is the type of a large American family in which the upper molars are selenodont and usually have four columns, while the lower canine is approximated to the incisors and its form and function assumed by the first premolar. The last upper premolar is simpler than the molars. There is no flange to the angle of the mandible; and the feet have four digits. The affinities of this peculiar family are probably widely spread, but they may have been derived from the Anthracotheriidæ. The type genus has the full Eutherian dentition, but in some of the more specialised forms (Cyclopidius) the upper incisors may be wanting, and large vacuities occur in the lachrymal region. The generalised genus Protoreodon, of the Upper or Uinta Eocene, has five cusps on the upper molars, arranged as in the Anthracotheriidæ. The pollex is retained in the manus of the type genus.

The family may be divided into subfamilies as follows:—

• I. Upper molars with four columns.
  • 1. Orbits open, no lachrymal fossa, a diastema, the last upper premolar with two outer columns, outer wall of upper molars concave and inclined inwards.—Agriochœrinæ (Agriochœrus).
  • 2. Orbits closed, a lachrymal fossa, no diastema, the last upper premolar with one outer column; outer wall of upper molars flattened.—Cotylopinæ (Cotylops, Eporeodon, Merycochœrus, Cyclopidius, etc.)
• II. Upper molars with five columns.—Protoreontinæ (Protoreodon).

Anoplotheriidæ.—This family includes several Upper Eocene European genera, with selenodont upper molars, carrying five columns arranged as those in Anthracotherium. One of the earliest known, Anoplotherium, was fully described by Cuvier from remains found in the Paris gypsum-beds (Upper Eocene). Its forty-four teeth formed a series unbroken by a gap or diastema, and were of uniform height (as in Man alone of existing mammals). Its tail was long, with large chevron bones underneath, not usually found in Ungulates, and there were either three or two toes on each foot. It was in many respects a much-specialised form, apparently not on the line of descent of any of the existing groups.

Dacrytherium is an allied genus whose dentition leads on to that of the smaller Xiphodon. The latter genus is characterised by the compressed and elongated form of the crowns of the first three premolars, which thus approximate to those of the Chevrotains. There were only two functional digits to the feet. The so-called Hyopotamus picteti, of the Swiss Eocene, is a species of Dacrytherium.

Cænotheriidæ.—The typical representatives of this family are small animals not larger than the Chevrotains, with the full complement of teeth, generally no marked gap in the series, and the crowns of the upper molars carrying two columns on the anterior and three on the posterior half of the crown—precisely the reverse of the arrangement obtaining in the Anthracotheriidæ. The known forms are from the Upper Eocene and Lower Miocene of Europe. In Cænotherium the molars are selenodont, while they are bunodont in Dichobunus. Homacodon, of the Bridger Eocene of the United States, is closely allied to the latter. The first lower premolar of Dichobunus assumes the form and function of a canine. Spaniotherium (Metriotherium) is a much larger form, in which the molars are not unlike those of Anthracotherium, if the arrangement of the cusps were reversed; it occurs in the Eocene Phosphorites of France. It is suggested that the Tylopoda may have originated from this group.

Tapirulus is a small Eocene Artiodactyle with the columns of the upper molars, which are somewhat like those of Hyopotamus, tending to form transverse ridges; its family position is uncertain.

Dichodontidæ.—The European genera included in this family all have quadritubercular selenodont molars, and show signs of approximating more or less closely to existing types. Dichodon, from the Upper Eocene and Lower Miocene, has the full complement of teeth, which show no diastema, and have low crowns. The fourth upper premolar has four columns, like the true molars, and the corresponding lower tooth three complete lobes; these features being unknown in any other Selenodonts. In Lophiomeryx, of the same beds, the somewhat higher crowns of the molars approximate to those of the Cervidæ, but the hinder lobes of the upper ones are imperfectly developed; the genus may be allied, to the Tragulidæ. In the small Gelocus, of the Lower Miocene, the molars are not unlike those of Dichodon; but the navicular and cuboid bones of the tarsus were fused together, and the metatarsals had united to form a “cannon-bone,” although the metacarpals still remained distinct. It is not improbable that upper incisors were wanting; and it has been suggested that we have in this genus the ancestral type of the Tragulidæ and Cervidæ.

Tylopoda.

Family Camelidæ.

This group is represented at the present day by the two species of Camels of the Old World and the Llamas of South America, collectively constituting the family Camelidæ. The special characters which the Llamas and Camels have in common, and the combination of which distinguishes them from the rest of the Artiodactyles, are as follows. The premaxillæ have the full number of incisor teeth in the young state, and the outermost is persistent through life as an isolated laniariform tooth. The canines are present in both jaws, and those of the mandible are differentiated from the long, procumbent, and spatulate incisors, being suberect and pointed. The crowns of the true molars belong to the crescentic or selenodont type, and are very hypsodont; but one or more of the anterior premolars is usually detached from the series, and is of simple pointed form. The auditory bulla is filled with cancellous tissue. The hinder part of the body is much contracted, and the femur long and vertically placed, so that the knee-joint is lower in position, and the thigh altogether more detached from the abdomen than in most quadrupedal mammals. The limbs are long, but with only the third and fourth digits developed; no traces of any of the others being present. The trapezoid and magnum of the carpus, and the cuboid and navicular of the tarsus are distinct. The two metapodial bones of each limb are confluent for the greater part of their length, though separated for a considerable distance at the lower end. Their distal articular surfaces, instead of being pulley-like, with deep ridges and grooves, as in other recent Artiodactyles, are simple, rounded, and smooth. The proximal phalanges are expanded at their distal ends, and the wide, depressed middle phalanges are embedded in a broad cutaneous pad, forming the sole of the foot, on which the animal rests in walking, instead of on the hoofs. The ungual phalanges are very small and nodular, not flattened on their inner or opposed surfaces, and not completely encased in hoofs, but bearing nails on their upper surface only. The cervical region is long and flexuous, and the vertebræ of which it is composed are remarkable for the position of the canal for the transmission of the vertebral artery, which does not perforate the transverse process, but passes obliquely through the anterior part of the pedicle of the arch (a condition only found in two other genera of mammals, Macrauchenia and Myrmecophaga). There are no horns or antlers. Though these animals ruminate, the stomach differs considerably in the details of its construction from that of the Pecora. The interior of the rumen or paunch has no villi on its surface, and there is no distinct psalterium or manyplies. Both the first and second compartments are remarkable for the presence of a number of pouches or cells in their walls, with muscular septa, and a sphincter-like arrangement of their orifices, by which they can be shut off from the rest of the cavity, and into which the fluid portion only of the contents of the stomach is allowed to enter.[186] The placenta is diffuse, as in the Suina and Tragulina, not cotyledonary, as in the Pecora. Finally, the Camelidæ differ not only from other Ungulates, but from all other mammals, in the fact that the red corpuscles of the blood, instead of being circular in outline, are oval, as in the inferior vertebrated classes.

Camelus.[187]—Dentition of adult: i ¹⁄₃, c ¹⁄₁, p ³⁄₂, m ³⁄₃; total 34. First upper premolar simple, placed immediately behind the premaxillæ, and separated by a long diastema from the penultimate tooth of that series. Lower incisors somewhat proclivous, the outermost the largest. Skull elongated, with an overhanging occiput, orbits completely surrounded by bone, and the premaxillæ not articulating with the arched and somewhat elongated nasals. Vertebræ: C 7, D 12, L 7, S 4, C 13-15. Ears comparatively short and rounded. One or two dorsal adipose humps. Feet broad, with the toes very imperfectly separated. Tail well developed, tufted at the end. Hair nearly straight, and not woolly. Size very large and bulky.

The genus is now represented by two species, viz. the single-humped Arabian Camel (Camelus dromedarius), and the double-humped Bactrian Camel (C. bactrianus, Fig. 114).[188] The former is quite unknown in a wild state, but it is reported that wild Bactrian Camels occur in the more remote parts of Turkestan. The latter species is found in a domesticated state throughout a large portion of Turkestan and the neighbouring region, extending as far as the Crimea in the west and to Lake Baikal and Pekin in the east. It is a heavier and more clumsy animal than the Arabian Camel, with thicker hair, shorter legs, and the feet more callous and better adapted to a hard ground. The hair is most developed upon the top of the head, neck, humps, arm, and wrist. Bactrian Camels are occasionally brought over the stupendous mountain passes south of Yarkand to within a few days’ journey of Leh, in Kashmir territory.

The Arabian Camel is commonly employed as a beast of burden in Africa and India, and has of late years been introduced into Australia for the same purpose; it is especially valuable in crossing long stretches of arid desert from its power of existing for a considerable period of time without water. The female goes fully eleven months with young, and produces but a single calf at a birth, which is suckled for a whole year. In disposition the Camel is surly and subject to furious outbursts of temper, especially during the rutting season. At such periods the male utters a peculiar and highly disagreeable bubbling noise in its throat, well known to all who have travelled in India with Camels as their transport. It has been said that the Camel is docile, but Palgrave observes:—

“If docile means stupid, well and good; in such a case the Camel is the very model of docility. But if the epithet is intended to designate an animal that takes an interest in its rider so far as a beast can, that in some way understands his intentions, or shares them in a subordinate fashion, that obeys from a sort of submissive or half-fellow-feeling with his master, like the horse or elephant, then I say that the camel is by no means docile—very much the contrary. He takes no heed of his rider, pays no attention whether he be on his back or not, walks straight on when once set agoing, merely because he is too stupid to turn aside, and then should some tempting thorn or green branch allure him out of the path, continues to walk on in the new direction simply because he is too dull to turn back into the right road. In a word, he is from first to last an undomesticated and savage animal, rendered serviceable by stupidity alone, without much skill on his master’s part, or any co-operation on his own save that of an extreme passiveness. Neither attachment nor even habit impress him; never tame, though not wide-awake enough to be exactly wild.” The two species breed together freely, and among the Yourouks of Asia Minor, hybrids, or mules, the produce generally of a male Bactrian and a female Arabian camel are preferred to either of the pure breeds.

Fossil remains of Camels are found in the Pliocene of the Siwalik Hills in Northern India. These differ from the existing representatives of the genus in having a vertical ridge at the antero-external angle of the lower molars, whereby they resemble Auchenia; their cervical vertebræ are also intermediate in structure between those of the latter and the existing Camels. A fossil Camel is also found in the Pleistocene of Algeria.

Auchenia.[189]—Dentition of adults normally: i ¹⁄₃, c ¹⁄₁, p ²⁄₂, m ³⁄₃; total 32—one of the lower premolars may, however, be wanting. In the upper jaw there is a compressed, sharp, pointed laniariform incisor near the hinder edge of the premaxilla, followed, in the male at least, by a moderate-sized, pointed, curved true canine in the anterior part of the maxilla. The isolated canine-like premolar which follows in the Camels is not present. The teeth of the molar series, which are in contact with each other, consist of two very small premolars (the first almost rudimentary) and three broad molars, constructed generally like those of Camelus. In the lower jaw the three incisors are long, spatulate, and procumbent; the outer ones being the smallest. Next to these is a curved, suberect canine, followed after an interval by an isolated, minute, and often deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of existing species of Camelus in having a small accessory column at the anterior outer edge. The skull generally resembles that of Camelus, the relatively larger brain-cavity and orbits and less developed cranial ridges being due to its smaller size. The nasal bones are shorter and broader, and are joined by the premaxillæ. Vertebræ: C 7, D 12, L 7, S 4, C 15-20. Ears rather long and pointed. No dorsal hump. Feet narrow, the toes being more separated than in the camels, each having a distinct plantar pad. Tail short. Hairy covering long and woolly. Size (in existing forms) smaller, and general form lighter than in the Camels. At present and within historic times the genus is entirely confined to the western side and southernmost parts of South America, but fossil remains have been found in the caves of Brazil, in the pampas of the Argentine republic, and in Central and North America.

The word Llama, sometimes spelt Lama, is the name by which the Peruvians designated one of a small group of closely allied animals, which, before the Spanish conquest of America, were the only domesticated hoofed mammals of the country, being kept, not only for their value as beasts of burden, but also for their flesh, hides, and wool,—in fact, supplying in the domestic economy of the people the place of the horse, the ox, the goat, and the sheep of the Old World. The word is now sometimes restricted to one particular species or variety of the group, and sometimes used in a generic sense to cover the whole. Although they were often compared by early writers to sheep, and spoken of as such, their affinity to the camel was very soon perceived, and they were included in the genus Camelus in the Systema Naturæ of Linnæus. They were, however, separated by Cuvier in 1800 under the name of Lama, changed by Illiger in 1811 to Auchenia (in allusion to the great length of neck, αὐχήν), a term afterwards adopted by Cuvier, and almost universally accepted by systematic zoologists, although there has been of late a disposition to revive the earlier name.

In essential structural characters, as well as in general appearance and habits, all the animals of this genus very closely resemble each other, so that the question as to whether they should be considered as belonging to one, two, or more species has been one which has led to a large amount of controversy among naturalists. The question has been much complicated by the circumstances of the great majority of individuals which have come under observation being either in a completely or partially domesticated state, and descended from ancestors which from time immemorial have been in like condition, one which always tends to produce a certain amount of variation from the original type. It has, however, lost much of its importance since the doctrine of the distinct origin of species has been generally abandoned.

The four forms commonly distinguished by the inhabitants of South America are recognised by some naturalists as distinct species, and have had specific designations attached to them, though usually with expressions of doubt, and with great difficulties in defining their distinctive characteristics. These are (1) the Llama, Auchenia glama (Linn.), or Lama peruana (Tiedemann); (2) the Alpaca, A. pacos (Linn.); (3) the Guanaco or Huanaco, A. huanacus (Molina); and (4) the Vicugna, A. vicugna (Molina), or A. vicunna, (Cuv.) The first and second are only known in the domestic state, and are variable in size and colour, being often white, black, or piebald. The third and fourth are wild, and of a nearly uniform light-brown colour, passing into white below. They certainly differ from each other, the Vicugna being smaller, more slender in its proportions, and having a shorter head (Fig. 116) than the Guanaco (Fig. 117). It may therefore, according to the usual view of species, be considered distinct. It lives in herds on the bleak and elevated parts of the mountain range bordering the region of perpetual snow, amidst rocks and precipices, occurring in various suitable localities throughout Peru, in the southern part of Ecuador, and as far south as the middle of Bolivia. Its manners very much resemble those of the Chamois of the European Alps; and it is as vigilant, wild, and timid. The wool is extremely delicate and soft, and highly valued for the purposes of weaving, but the quantity which each animal produces is not great.

The Guanaco has an extensive geographical range, from the highlands of the Andean region of Ecuador and Peru to the open plains of Patagonia, and even the wooded islands of Tierra del Fuego. It constitutes the principal food of the Patagonian Indians, and its skin is invaluable to them, as furnishing the material out of which their long robes are constructed. It is about the size of a European Red Deer, and is an elegant animal, being possessed of a long, slender, gracefully curved neck and fine legs. Dr. Cunningham,[190] speaking from observation on wild animals, says:—

“It is not easy to describe its general appearance, which combines some of the characters of a camel, a deer, and a goat. The body, deep at the breast but very small at the loins, is covered with long, soft, very fine hair, which on the upper parts is of a kind of fawn-colour, and beneath varies from a very pale yellow to the most beautiful snow-white. The head is provided with large ears, in general carried well back, and is covered with short grayish hair, which is darkest on the forehead. Occasionally the face is nearly black. As a rule it lives in flocks of from half a dozen to several hundreds, but solitary individuals are now and then to be met with. They are very difficult to approach sufficiently near to admit of an easy shot, as they are extremely wary, but, on being disturbed, canter off at a pace which soon puts a safe distance between them and the sportsman, even though he should be mounted. Despite their timidity, however, they are possessed of great curiosity, and will sometimes advance within a comparatively short distance of an unknown object, at which they will gaze fixedly till they take alarm, when they effect a speedy retreat. Their cry is very peculiar, being something between the belling of a deer and the neigh of a horse. It would be difficult to overestimate their numbers upon the Patagonian plains; for in whatever direction we walked we always came upon numbers of portions of their skeletons and detached bones.”

Darwin, who has given an interesting account of the habits of the Guanaco in his Naturalist’s Voyage, says that they readily take to the water, and were seen several times at Port Valdes swimming from island to island.

The Llama is only known as a domestic animal, and is chiefly met with in the southern part of Peru. Burmeister, a very competent writer on the subject, says that he is perfectly satisfied that it is the descendant of the wild Guanaco, an opinion opposed to that of Tschudi. It generally attains a larger size than the Guanaco, and is usually white or spotted with brown or black, and sometimes altogether black. The earliest and often-quoted account of this animal by Agustin de Zarate, treasurer-general of Peru in 1544, will bear repeating as an excellent summary of the general character and uses to which it was put by the Peruvians at the time of the Spanish conquest. He speaks of the Llama as a sheep, observing, however, that it is camel-like in shape though destitute of a hump:—

“In places where there is no snow the natives want water, and to supply this they fill the skins of sheep with water and make other living sheep carry them; for, it must be remarked, these sheep of Peru are large enough to serve as beasts of burden. They can carry about one hundred pounds or more, and the Spaniards used to ride them, and they would go four or five leagues a day. When they are weary they lie down upon the ground; and as there are no means of making them get up, either by beating or assisting them, the load must of necessity be taken off. When there is a man on one of them, if the beast is tired and urged to go on, he turns his head round and discharges his saliva, which has an unpleasant odour, into the rider’s face. These animals are of great use and profit to their masters, for their wool is very good and fine, particularly that of the species called Pacas, which have very long fleeces; and the expense of their food is trifling, as a handful of maize suffices them, and they can go four or five days without water. Their flesh is as good as that of the fat sheep of Castile. There are now public shambles for the sale of their flesh in all parts of Peru, which was not the case when the Spaniards came first; for when one Indian had killed a sheep his neighbours came and took what they wanted, and then another Indian killed a sheep in his turn.”

The disagreeable habit here noticed of spitting in the face of persons whose presence is obnoxious is common to all the group, as may be daily witnessed in specimens in confinement in the menageries of Europe. One of the principal labours to which the Llamas were subjected at the time of the Spanish conquest was that of bringing down ore from the mines in the mountains. Gregory de Bolivar estimated that in his day as many as three hundred thousand were employed in the transport of the produce of the mines of Potosi alone; but since the introduction of horses, mules, and donkeys the importance of the Llama as a beast of burden has greatly diminished.

The Alpaca, though believed by many naturalists to be a variety of the Vicugna, is more probably, like the Llama, derived from the Guanaco, having the naked callosities on the hind limbs, and the relatively large skull of the latter. It is usually found in a domesticated or semi-domesticated state, being kept in large flocks which graze on the level heights of the Andes of southern Peru and northern Bolivia at an elevation of from 14,000 to 16,000 feet above the sea-level, throughout the year. It is smaller than the Llama, and, unlike that animal, is not used as a beast of burden, but is valued only for its wool, of which the Indian blankets and ponchas are made. Its colour is usually dark brown or black.

Mention has already been made of the occurrence of fossil Llamas in America, but some diversity of view obtains as to the generic position of some of these forms, owing to variations in their dental formula. Remains apparently referable to the existing species occur in the cavern-deposits of Brazil. In the Pleistocene of Mexico we meet with A. (Palauchenia) magna, which attained the size of a Camel, and had always two, and occasionally three, lower premolars; while in one South American Pleistocene species, which has been generically separated as Hemiauchenia, there were invariably three premolars in each jaw. In A. (Holomeniscus) hesterna, from the Pleistocene of North America, which was equal in size to A. magna, the premolars were reduced to one in each jaw; and the same condition obtains in A. (Eschatius) vitakeriana, where, however, the upper one is of simpler structure.

Extinct Cameloids.—Until within the last few years the existence of two genera having so very much in common as the Camels and the Llamas, and yet so completely isolated geographically, had not received any satisfactory explanation; for the old idea that they in some way “represented” each other in the two hemispheres of the world was a mere fancy without philosophical basis. The discoveries made mostly within the past twenty years of a vast and previously unsuspected extinct fauna in the American continent of the Tertiary period, as interpreted by Leidy, Cope, Marsh, and others, has thrown a flood of light upon the early history of this family, and upon its relations to other mammals.

There have been found in these regions many Camel-like animals exhibiting different generic modifications; and, what is more interesting, a gradual series of changes, coinciding with the antiquity of the deposits in which they are found, have been traced from the thoroughly differentiated species of the modern epoch down through the Pliocene to the early Miocene beds, where, their characters having become by degrees more generalised, they have lost all that specially distinguishes them as Camelidæ, and are merged into forms common to the ancestral type of all the other sections of the Artiodactyles. Hitherto none of these annectant forms have been found in any of the fossiliferous strata of the Old World; and it may therefore be fairly surmised (according to the evidence at present before us) that America was the original home of the Tylopoda, and that the true Camels have passed over into the Old World, probably by way of the north of Asia, where we have every reason to believe there was formerly a free communication between the continents, and then, gradually driven southward, perhaps by changes of climate, having become isolated, have undergone some further special modifications; while those members of the family that remained in their original birthplace have become, through causes not clearly understood, restricted solely to the southern or most distant part of the continent. The occurrence in the dentition of the fossil Siwalik Camels of a feature now found only in Auchenia is especially interesting from this point of view.

Briefly referring to some of these fossil types, we may note that Pliauchenia, of the Loup Fork beds (Lower Pliocene) of the United States, has three lower premolars, while in Procamelus there were four of these teeth. In Protolabis of the Miocene we have a more generalised form, in which the dental formula is i ³⁄₃, c ¹⁄₁, p ⁴⁄₄, m ³⁄₃; and from this type a transition may be traced to Poëbrotherium, which, while having the same dental formula, was no larger than a Fox, and had the third and fourth metacarpals separate, with rudiments of the fourth and fifth. The earliest undoubted representative of the group is Leptotragulus, of the Uinta Eocene, which appears to have been closely allied to Poëbrotherium. It is, however, probable that the first lower premolar was wanting; while the other premolars of the mandible were much shorter antero-posteriorly than in the last-named genus. The manus, moreover, appears to have been less reduced, the second metacarpal retaining its connection with the magnum. It is suggested that Leptotragulus may have been derived from the Bunodont genus Homacodon of the Bridger Eocene, mentioned among the Cænotheriidæ.

Tragulina.

Family Tragulidæ.

No teeth in premaxillæ. Upper canines well developed, especially in the males; narrow and pointed. Lower canines incisiform. No caniniform premolars in either jaw, all the premolars except the last in the upper jaw being secant. Molariform teeth in a continuous series, consisting of p ³⁄₃, m ³⁄₃. Odontoid process of axis vertebra conical. Fibula complete. Four complete toes on each foot. The middle metapodials generally confluent, the outer ones (second and fifth) very slender but complete, i.e. extending from the carpus or tarsus to the digit. Navicular, cuboid, and ectocuneiform bones of tarsus united. Tympanic bullæ of skull filled with cancellar tissue. No frontal appendages. Ruminating, but the stomach with only three distinct compartments, the manyplies or third cavity of the stomach of the Pecora being rudimentary. Placenta diffused.

This section is represented only by the single family Tragulidæ, containing a few animals of small size, commonly known as Chevrotains, intermediate in their structure between the Deer, the Camels, and the Pigs. The large size of the canines of the male and the absence of horns caused them to be associated formerly with Moschus, one of the Cervidæ; hence they are often spoken of as “Pigmy Musk-Deer,” although they have no musk-secreting gland, or, except in the above-named trivial external characters, no special affinities with the true Musk-Deer. There has scarcely been a more troublesome and obdurate error in zoology than in this association of animals so really distinct. It has been troublesome, not only in preventing a just conception of the relations of existing Artiodactyles, but also in causing great confusion and hindrance in palæontological researches among allied forms; and most obdurate, inasmuch as all that has been recently done in advancing our knowledge of both groups has not succeeded in eradicating it, not only from nearly every one of our zoological text-books, whether British or Continental, but even from works of the highest scientific pretensions.

The family is now generally divided into two genera.

Tragulus,[191] containing the smallest of the existing Ungulates, animals having more of the general aspects and habits of some Rodents, as the Agoutis, than of the rest of their own order. The best-known species are T. javanicus, T. napu, T. stanleyanus, and T. memmina. The first three are from the Malay Peninsula, or the islands of the Indo-Malayan Archipelago, the last from Ceylon and India. A fossil species occurs in the Pliocene of the latter country.

Dorcatherium[192] is distinguished chiefly by the feet being stouter and shorter, the outer toes better developed, and the two middle metacarpals not ankylosed together. Its dental formula (as that of Tragulus) is usually i ⁰⁄₃, c ¹⁄₁, p ³⁄₃, m ³⁄₃ = 34. Vertebræ: C 7, D 13, L 6, S 5, C 12-13. The only existing species, D. aquaticum (Fig. 118), from the west coast of Africa, is rather larger than any of the Asiatic Chevrotains, which it otherwise much resembles, but it is said to frequent the banks of streams, and have much the habits of Pigs. It is of a rich brown colour, with back and sides spotted and striped with white. It is evidently the survivor of a very ancient form, as remains of the type species (D. naui), only differing in size, occur in the lower Pliocene and Miocene of Europe; fossil species are also found in the Indian Pliocene. In D. naui there are, at least frequently, four lower premolars, while the existing species has but three of these teeth.

Extinct Traguloids.—A number of small selenodont Artiodactyles from various Miocene and Pliocene deposits appear to connect the modern Tragulina so closely with Gelocus (p. 294), and thus with the ancestral Cervidæ, that their classification is almost an impossibility. Thus Leptomeryx, from the Miocene of the United States, is regarded as a Traguloid, having four premolars in each jaw and with the metatarsals fused into a cannon-bone. Prodremotherium, of the Upper Eocene Phosphorites of France, differs in that the metacarpals also form a cannon-bone; while in the American Hypertragulus, both metacarpals and metatarsals remain separate. Bachitherium, of the French Phosphorites, apparently presents affinity with Gelocus, Prodremotherium, and Dorcatherium. In this genus the first of the four lower premolars assumes the character and function of a canine, the true canine being incisor-like, and there are traces of minute upper incisors.

Pecora, or Cotylophora.

No premaxillary teeth or caniniform premolars. Upper canines generally absent, though sometimes largely developed. Inferior incisors, three on each side with an incisiform canine in contact with them. Molariform teeth consisting of p ³⁄₃, m ³⁄₃, in continuous series. Auditory bullæ simple and hollow within. Odontoid process in the form of a crescent, hollow above. Distal extremity of the fibula represented by a distinct malleolar bone of peculiar shape, articulating with the outer surface of the lower end of the tibia. Third and fourth metacarpals and metatarsals confluent. Outer or lateral toes small and rudimentary, or in some cases entirely suppressed; their metapodial bones never complete in existing forms. Navicular and cuboid bones of tarsus united. Horns or antlers usually present, at least in the male sex. Left brachial artery arising from a common innominate trunk, instead of coming off separately from the aortic arch as in the preceding sections. Stomach with four complete cavities. Placenta cotyledonous.[193]

The Pecora or true Ruminants form at the present time an extremely homogeneous group, one of the best-defined and most closely united of any of the Mammalia. But, though the original or common type has never been departed from in essentials, variation has been very active among them within certain limits; and the great difficulty which all zoologists have felt in subdividing them into natural minor groups arises from the fact that the changes in different organs (feet, skull, frontal appendages, teeth, cutaneous glands, etc.) have proceeded with such apparent irregularity and absence of correlation that the different modifications of these parts are most variously combined in different members of the group. It appears, however, extremely probable that they soon branched into two main types, represented in the present day by the Cervidæ and the Bovidæ,—otherwise the antlered and horned Ruminants. Intermediate smaller branches produced the existing Musk-Deer and Giraffe, as well as the extinct Helladotherium inclining to the first-named group, and the extinct Sivatherium, Brahmatherium, Hydaspitherium, and others more allied to the latter, although upon the true relationship of these forms there is a difference of opinion.

The earliest forms of true Pecora, as Palæomeryx, generally had no frontal appendages, and some few forms continue to the present day in a similar case. In the very large majority, however, either in both sexes or in the male only, a pair or occasionally two pairs (Tetraceros and the extinct Sivatherium) of processes are developed from the frontal bones as weapons of offence and defence, these being almost always formed on one or other of two types.

1. “Antlers” are outgrowths of true bone, covered during their growth with vascular, sensitive integument coated with short hair. When the growth of the antler is complete, the supply of blood to it ceases, the skin dies and peels off, leaving the bone bare and insensible, and after a time, by a process of absorption near the base, it becomes detached from the skull and is “shed” (Fig. 119). A more or less elongated portion or “pedicle” always remains on the skull from the summit of which a new antler is developed. In the greater number of existing species of Deer this process is repeated with great regularity at the same period of each year. The antler may be simple, straight, subcylindrical, tapering and pointed, but more often it sends off one or more branches called “tines” or “snags” (Fig. 119). In this case the main stem is termed the “beam.” Commonly all the branches of the antler are cylindrical and gradually tapering. Sometimes they are more or less expanded and flattened, the antler being then said to be “palmated.” In young animals the antlers are always small and simple, and in those species in which they are variously branched or palmated, this condition is only gradually acquired in several successive annual growths. An interesting parallel has been observed here, as in so many other cases, between the development of the race and that of the individual. Thus the earliest known forms of Deer, those of the Lower Miocene, generally have no antlers, as in the young of the existing species. The Deer of the Middle Miocene have simple antlers, with not more than two branches, as in existing Deer of the second year; but it is not until the Pliocene and Pleistocene times that Deer occur with antlers developed with that luxuriance of growth and beauty of form characteristic of some of the existing species in a perfectly adult state. Among recent Cervidæ, antlers are wanting in the genera Moschus and Hydropotes; they are present in both sexes in Tarandus (the Reindeer), and in the male sex only in all others.

In those forms with the most complex antlers (Figs. 119, 120) the tine immediately over the forehead is termed the brow tine, the next one the bez tine, and the third one the tres tine; the mass of points at the summit of the antler being termed either the royal and surroyal tines, or collectively the crown. The nodulated bony ring at the base of the antler, just above the point at which it separates from the pedicle when it is shed, is termed the burr.