Chapter XI: UNGULATA (continued)--ARTIODACTYLA (EVEN-TOED UNGULATES)--SIRENIA (1)

SUB-ORDER 10. ARTIODACTYLA.

FIG. 138.--Bones of the Manus--A, of Pig (_Sus scrofa_). x 1/3. B, of Red Deer (_Cervus elaphus_). x 1/2. C, of Camel (_Camelus bactrianus_). x 1/8. _c_, Cuneiform; _l_, lunar; _m_, magnum; _m_^2, _m_^5, second and fifth metacarpals; _R_, radius; _s_, scaphoid; _td_, trapezoid; _u_, unciform; _U_, ulna; _II-V_, second to fifth fingers. (From Flower's _Osteology_.)

The Artiodactyle or "Even-toed" Ungulates are to be distinguished from the Perissodactyla, and from other Ungulate groups, by a number of trenchant characters. The most salient {270} of these, and that which has given its name to the group, concerns the arrangement of the digits. Instead of there being but one prevailing digit--the third, in the hand and foot, through which the axis of the foot passes, there are two, numbers three and four, between which the same axis passes, and which are perfectly symmetrical with each other. This type of foot has been termed "paraxonic," as opposed to the "mesaxonic" Perissodactyle foot (see Fig. 121 B, p. 235). It has been attempted to prove that the single prevailing digit of the Horse's foot is a fused pair of digits, and the state of affairs which characterises the Camel, where the two metacarpals or metatarsals are to an almost complete extent united, has been urged in proof; so, too, certain abnormalities, such as those called "solid-hoofed pigs."[179] These latter are simply Pigs in which the two central metacarpals and the terminal hoofs are completely fused with one another. In some of such cases there is not the slightest trace of the union of the separate metacarpals and phalanges. Even the sesamoid bones, attached behind to the toes, are two in number instead of four. And, furthermore, the tendon supplying the bones is single, though showing traces of its double origin. Such Pigs often show the abnormality from generation to generation, and they proved convenient for those whose scruples would not allow them to eat the flesh of a beast "dividing the hoof" and not chewing the cud. More singular still, as showing a pathological approach from another side to the Perissodactyle condition in an Artiodactyle, is a calf, where the foot ended in three equi-sized digits, of which the middle one lay in the longitudinal axis of the limb. From the opposite side cases are known of a Horse with a split hoof and phalanges, thus presenting the most striking likeness to a Camel.

There is, furthermore, in certain groups of Artiodactyles (_e.g._ the Tragulidae) a tendency for the two middle metacarpals to unite, quite apart from such "sports" as those illustrated by the cases just set forth. And, as already mentioned, the union of the two middle metacarpals culminates in the Camel, Ox, etc. There is, however, absolutely no trace of such a fusion in the series of Perissodactyle animals known to us; and it would be by fusion rather than dismemberment that, as it would appear on this theory, the modern Ungulate foot has been arrived at. Of course {271} the facts of Ungulate descent are absolutely destructive of any such comparisons.

As is the case with the Perissodactyles, the Artiodactyles show a historical series, the primitive five-toed condition being almost preserved in _Oreodon_, up to the most modern modification exemplified by the Ox, Sheep, etc., in which animals there are not even vestiges of the fourth and fifth toes. It has been stated, however, that the foetal Sheep has traces of those rudiments. The so-called cannon bone (the fused third and fourth metapodia) is accompanied in its fusion by an increase in length. At the same time the functional middle metacarpals push aside the rudiments and, forming a broad surface for that purpose, articulate with the magnum and unciform bones to the exclusion of the rudiments. This has been termed an "adaptive reduction." In the "inadaptive reduction" there is the same reduction of the metacarpals, but the rudiments still articulate as in the primitive Artiodactyle foot, _i.e._ Mc II with trapezium, trapezoid, and magnum; Mc III with magnum and unciform; Mc IV and V with unciform. This would appear to give greater solidity and consequently greater strength to the foot.

FIG. 139.--Dorsal surface of right tarsus of Red Deer (_Cervus elaphus_). x 1/3. _a_, Astragalus; _c_, calcaneum; _c_^3, cuneiform; _cb_, cuboid; _mIII_, _mIV_, metatarsals; _n_, navicular. (From Flower's _Osteology_.)

The carpal bones of the Artiodactyla alternate in their articulation; the primitive state of affairs[180] is not retained even in the earliest types. The femur has no third trochanter, so prevalent in the Perissodactyles. In the hind-foot the calcaneum has an articular facet for the fibula, which is not characteristic of the Perissodactyla. In the more modern forms, _e.g._ the Cervidae, the navicular and cuboid become fused into one bone; and there are even further fusions which will be referred to later as characteristic features of different groups. It is interesting to notice that the reduction begins earlier and is clearer in the hind-foot than in the fore. One {272} can see how this may be purely adaptive, the push of the hind-legs in running needing a firmer support. In _Hyomoschus_ this is the case. The hind-limbs are provided with a cannon bone, while the metacarpals of the fore-feet are still free.

The number of dorso-lumbar vertebrae is less in the Artiodactyle than in the Perissodactyle Ungulates. Whereas the former have but nineteen, the latter have, as a rule, twenty-three such vertebrae.[181] The number of ribs varies from twelve (_Camelus_, _Hydropotes_) through thirteen (_Cervus_, _Gazella_) to fourteen in _Dicotyles_, _Giraffa_, etc.

The curious form of teeth known as "selenodont" is characteristic of the Artiodactyla, though only found well developed in the modern forms, and of those only in the Pecora. The more primitive forms had "bunodont" teeth with typically four tubercles (if we except the tritubercular and but little-known _Pantolestes_); and the intermediate "buno-selenodont" type characterises such groups as the Anthracotheriidae.

While the stomach of the Perissodactyles is always a simple sac, it is complicated, or shows signs of complication, in the Artiodactyles. That of the Hippopotamus is divided into two chambers; there are three in _Tragulus_, and four in the typical Ruminants such as _Cervus_, _Ovis_, etc.

Had we to deal only with the still living genera of Artiodactyles, it would be easy to sort them into two groups on the characters of the teeth; for the Pigs and Hippopotamus are provided with tubercular molars; they are bunodont. The Deer, Camels, Oxen, Giraffes, etc., have selenodont molars. Besides, the latter are "Ruminants," and have a more complicated stomach. The existing Chevrotains forbid a more trenchant division, since they are, as will be pointed out in due course, somewhat intermediate in structure; the feet are more Pig-like, and the stomach is not so typically Ruminant. In any case such a division is prevented by certain extinct families which are perhaps ancestral to both. They have teeth which are not quite bunodont and not quite selenodont. These teeth have been termed buno-selenodont or buno-lophodont.

The distribution of the living Artiodactyles presents us with some interesting facts. The vast preponderance of species occurs in the Old World--34 in America as against over 250 species {273} in Europe, Asia, and Africa. The Neotropical region has no Oxen, or Sheep, or Antelopes. The latter are confined to Africa, Asia, and certain parts of the Palaearctic region; they are vastly more prevalent in Africa, where they take the place of the totally absent Deer. The Pig tribe is almost entirely Oriental and Ethiopian in distribution, only one form, the European Wild Boar, ranging into the Palaearctic region; and the two species of Peccary are found in both North and South America. Broadly speaking, the Ethiopian region is the headquarters of the Artiodactyla. But the great island of Madagascar has but one form of Artiodactyle, a Pig of the genus _Potamochoerus_.[182]

GROUP I.--_SUINA._

FAM. 1. HIPPOPOTAMIDAE.--The family Hippopotamidae contains of existing genera only _Hippopotamus_, for the Liberian dwarf Hippopotamus is not now regarded, as it was formerly, as the type of another genus, _Choeropsis_. The reasons for its former separation were the loss of the outer pair of incisors and the different proportions of various parts of the skull. This little Liberian animal has, however, been shown by Sir W. Flower[183] to possess the missing incisors occasionally; and as to the proportions of the skull, it is exceedingly common for small animals to vary from larger relatives in this way. Hence, considering the characteristic features of the Hippopotamus and the fewness of species, it seems unnecessary to divide it up further. We shall therefore only recognise one genus.

The Hippopotamus at present is African in range, and confined to that continent. But quite recently it inhabited Madagascar; and further back still in time the existing African species, _H. amphibius_, ranged into Europe; there were also Indian forms, which were contemporary with the Stone-age man. The Common Hippopotamus is a great thick-skinned beast with but few hairs. It has four toes on each foot, a complex stomach, but no caecum. The strong incisors continue growing through life, as do the great canines. The number of incisors is two on each side of each jaw. Some of the extinct species had six in each {274} jaw, and they were distinguished as a genus _Hexaprotodon_, contrasting with _Tetraprotodon_, until intermediate conditions were observed. _Choeropsis_, as already observed, was a still further reduction of the tetraprotodont type. The molars (the formula is Pm 4/4 M 3/3) when worn show a double trefoil pattern. The orbital cavity is encircled by bone. As with many other aquatic mammals the kidneys are lobulated.

FIG. 140.--Hippopotamus. _Hippopotamus amphibius._ x 1/40.

A very singular fact about the Hippopotamus is the production of a "bloody sweat," a carmine-coloured secretion, containing small crystals and corpuscles, from the skin. This coloured fluid has of course nothing to do with blood.[184]

The animal grows to a length of at any rate 14 feet. The limbs and the tail are short. Like other aquatic animals the nostrils are on the surface of the head, and can be closed when the animal is under water. When it reaches the surface of the water after a prolonged immersion, it spouts like a Whale. Sir Samuel Baker says that ten minutes is the longest time that the Hippopotamus can remain below the water. It is frequently a dangerous animal to encounter, as it will capsize boats, and even bite large pieces out of their bottoms; with its huge teeth it {275} can and does attack and destroy human beings. The Hippopotamus not only swims, but can walk along the bottom of a river with great rapidity. It occasionally puts out to sea from the mouths of rivers frequented by it; and it is supposed that in this way Madagascar was populated with Hippopotamuses, whose remains are now found in swamps in that island.

FIG. 141.--Wild Boar. _Sus scrofa._ x 1/12.

FAM. 2. SUIDAE.--The Pig family, Suidae, differ from the last in their smaller size, in the terminal nostrils and mobile snout, which is not grooved, except faintly as in _Babirusa_. They are generally hairy, but the Babyroussa is an exception, while _Phacochoerus_ is but slightly haired. Though there are four digits, as in the Hippopotamus, only two reach the ground in walking. The stomach, furthermore, is simple, and (except in _Dicotyles_) there is a caecum. The kidneys are smooth, and the liver is more lobate than in _Hippopotamus_. The orbital cavity is confluent with the temporal fossa. The typical genus, _Sus_, is distributed over Europe, Asia, and the islands of the Malay Archipelago, reaching as far as Borneo and Celebes. The dentition[185] is complete. A single species, the so-called _S. sennaariensis_, is from Ethiopian Africa, but it is not certain how far this animal may be an escaped species introduced by man. A very large number of "species" of _Sus_ have been described, but Dr. Forsyth {276} Major is disposed to reduce them to four if not to fewer species. He allows the widely-ranging _S. scrofa_, _S. vittatus_, and the eastern Malayan _S. verrucosus_ and _S. barbatus_.

FIG. 142.--Pygmy Hog (from _Nature_). _Sus salvania._ x 1/6.

The Pygmy Hog of the Bhotans seems to be not entitled to specific rank, certainly not to generic (in the opinion of some), though it has been termed _Porcula salvania_.[186] The Wild Boar of Europe is _Sus scrofa_. It was formerly quite abundant in this country; not merely are its remains exhumed from fens, caves and peat bogs, but there is ample evidence of its continuance down to a comparatively late historic period. Enactments are on record as to the hunting of these animals; there are places, such as Boarstall, whose names are clearly derived from the name of the animal, presumably once a native of the locality; and various documents all show the presence of the Wild Boar {277} in this country down to so late a period as the end of the sixteenth century.

FIG. 143.--Wart Hog. _Phacochoerus aethiopicus._ x 1/6.

The African Wart Hog, genus _Phacochoerus_, is usually regarded as the type of a distinct genus of Pigs. This animal, "superlatively ugly" with its huge tusks and great protuberances upon the face, is chiefly to be distinguished from the genus _Sus_ by these characters, and by the complexity of the last molar, which, with the tusks, are sometimes in aged animals the only teeth left. The complete formula is Pm 2/2 M 3/3. There are two species of this genus, _P. aethiopicus_ and _P. africanus_. When enraged the Wart Hog is said to carry its tail directly up, and to present a ludicrous as well as ferocious appearance.

FIG. 144.--Head of Wart Hog.

The Celebesian Babyroussa, genus _Babirusa_, is an almost hairless hog with enormously upturned tusks in both jaws of the {278} male. In the Wild Boar there is a hint of this, which is carried still further in _Phacochoerus_; but in _Babirusa_ the upper tusks turn upwards before they leave the substance of the jaw, for which reason they appear to arise on its dorsal surface; the lower tusks are nearly as long. It has been found that the young of this Pig are not striped as are those of other Pigs. By means of the curved upper tusks this animal has been said by old writers to suspend itself to branches of trees, just as does by his downwardly-projecting tusks the male Chevrotain! There is but one species, _B. alfurus_.

From _Sus_ proper the African and Malagasy _Potamochoerus_, including the Red River Hog, is barely separable generically. Their principal claim to generic distinction lies in the existence of a horny outgrowth arising from a bony apophysis above the canine in the male. These have been compared to the osseous "horn cores" in the extinct Dinocerata. But the Javan _Sus verrucosus_ shows at least the beginning of a similar modification. The popular name of the animal is derived from the fine rufous colour of its pelage, not seen, however, in all the species. Dr. Forsyth Major[187] recognises five species, of which only one is from Madagascar.

FIG. 145.--Peccary. _Dicotyles tajacu._ x 1/6.

FAM. 3. DICOTYLIDAE.--The Peccaries are generally placed in a different family from that of the other Pigs. This family, {279} Dicotylidae, contains but one genus, _Dicotyles_, with at most two species. The name of the animal is connected with the dorsal gland; the animal thus appeared to possess two navels. The Peccaries, exclusively confined to the New World, differ from the Old-World Pigs in one or more important characters. They have only three toes on the hind-feet, and the stomach is complicated. Though the Peccaries have but small tusks they hunt in packs and are very dangerous animals to meet with. They owe, too, their safety from many foes to their sociable habits. Being nocturnal animals they are liable to the attacks of the Jaguar, which will speedily overpower and devour a Peccary that has strayed from its herd.

FOSSIL SWINE.--The existing genera of the Pig tribe are also known in a fossil condition. _Sus_ itself goes back as far as the Upper Miocene. _Sus erymanthius_, the Erymanthine Boar, is known from beds of that age in Greece, England, and Germany. This genus is not known to have had a wider distribution in the past than it has in the present. _Dicotyles_ occurs in the Pleistocene of both North and South America, the regions which it inhabits at the present day. The genus _Listriodon_, also Miocene, is remarkable for having lophodont instead of bunodont teeth, that is so far as concerns the molars, which resemble those of the Tapir. It was European and Indian in range. A number of genera, more remote from the existing Pigs than those which have just been dealt with, are placed together in a special sub-family, Achaenodontinae. The type genus, _Achaenodon_, had a somewhat short skull for a Pig; and it is in general aspect and in the characters of the canine teeth highly suggestive of that of a Carnivore. The bunodont molars, however, are Suine, as is the form of the lower jaw with a rounded angle. This is an Eocene animal found in Wyoming.

_Elotherium_[188] occurs chiefly in the Miocene of both North America and Europe; but _E. uintense_ is Eocene. The orbits are completely encircled by bone in the more modern forms; this is not the case in the last-described genus, with which _E. uintense_ agrees. The skull is also longer and more Pig-like. The zygomatic arch is powerful, with sometimes a large descending process, such as is found in _Diprotodon_, more faintly in Kangaroos, and in Sloths and certain extinct Edentates. The lower jaw has a pair {280} of dependent processes near the symphysis, which suggest processes occupying a corresponding position in _Dinoceras_. The skull and body are heavy, but the two-toed limbs are slender. There is a smaller pair of toes behind these. The dentition is complete, and the canines are not inordinately developed. The brain is very diminutive. Perhaps _E. uintense_ should be separated as a distinct genus, _Protelotherium_.[189]

_Hyotherium_ (which is regarded as identical with _Palaeochoerus_) has a sharp sagittal crest; the orbit is nearly but not quite closed. The canines are not strongly developed. The upper canines have double fangs as in _Triconodon_ among extinct mammals, and as in the Hedgehog and other forms among living Mammalia. The premolars have the cutting and serrated edge of those of some other Pigs, a feature which gives them a curious resemblance to the "grinding" teeth of Seals. The molars are tuberculate, and like those of living Pigs. It is European and Indian in range, and Miocene.

The genus _Choeropotamus_ has a complete dental formula save for the loss of a premolar in the lower jaw. Though it has lost this tooth, it is from an older stratum than some of those forms which have retained that premolar; it has been found in the Upper Eocene of the Isle of Wight and of the neighbourhood of Paris.

The American and Miocene _Chaenohyus_ has lost the corresponding teeth of the upper jaw.

_Homacodon_[190] is a genus consisting of several species, which has a bunodont and complete dentition. The molars are sextubercular in the upper jaw. _H. vagans_ was of about the size of a Rabbit, and it appears to have had a curved neck. The limbs had five digits, as is so generally the case with Eocene Ungulates. It is known from the Middle Eocene of Wyoming.

GROUP II.--_RUMINANTIA._

The Selenodontia or Ruminantia form the second division of existing Artiodactyles. The characters of the teeth, which give them their name, have already been referred to. They also differ in that there are never more than a single pair of incisors {281} in the upper jaw, and very usually there are none. As a general rule the third and fourth metacarpals and metatarsals become united to form a cannon bone. To this there is but one exception, the African _Hyomoschus_. Moreover, the second and fifth digits are nearly always rudimentary, and may practically disappear altogether. Here again the Tragulidae are an exception. The Ruminantia are so-called on account of the fact that they "ruminate," that is, after the food has been rapidly swallowed, it is forced back up the gullet and more thoroughly masticated. Associated with this is a complex stomach, which is divided into several compartments. This stomach has at least three compartments, as in the Tragulidae; but it has usually four. Its characters are illustrated in Fig. 146. The majority of the Selenodontia possess horns, which are partly formed of solid protuberances of the frontal bones. In the Giraffe they are somewhat different.

FIG. 146.--Stomach of Ruminant opened to show the internal structure. _a_, Oesophagus; _b_, rumen; _c_, reticulum; _d_, psalterium; _e_, abomasum; _f_, duodenum. (After Flower and Lydekker.)

This group may be divided into--A. TRAGULINA, Chevrotains; B. TYLOPODA, Camels, Lamas; and C. PECORA, Deer, Antelopes, Oxen, Giraffes, Goats, Sheep.

A. TRAGULINA.

As the Tragulina are undoubtedly the most ancient of the Selenodontia it will be logical to commence with an account of them. {282}

FAM. 4. TRAGULIDAE.--This family comprises a number of small Deer-like animals, which are really in many points more related to the Pigs than to the true Deer. They are known as Chevrotains; and the term "Deerlet," introduced by Professor Garrod, is certainly appropriate, since they have the aspect of very small and hornless Deer. If it were not for their Artiodactyle feet one might at a glance confuse these creatures with some Marsupial type. The family is Oriental and West African in range. The two genera (whose individual peculiarities will be considered later) differ from other Artiodactyles in a number of rather important characters.

FIG. 147.--Indian Chevrotain. _Tragulus meminna._ x 1/4.

They are absolutely hornless in both sexes. The canines are present in both jaws, and are especially well developed in the upper jaw. The dental formula is I 0/3 C 1/1 Pm 3/3 M 3/3. In the skull the tympanic bulla is usually, as in the non-ruminating Artiodactyles, filled with loose bony tissue. The feet (usually) have the four toes of the Suina, and are therefore in a more primitive condition than in Deer and Antelopes. But as the middle metacarpals are fused in _Tragulus_ (though separate in _Hyomoschus_) they are a stage further than are the Pigs, in the direction of the typical Ruminants.

The stomach is comparatively simple, thus offering {283} intermediate characters between the Pigs and the Ruminants; there are but three separate compartments. A highly-interesting character is afforded by the placenta. This is in the present family of the diffuse kind, not presenting the separated and tufted cotyledons of the Ruminant placenta. This we may fairly assume is a further proof of the less-specialised characters of this group[191] as compared with the Ruminantia, a view, however, which is not universally accepted. While the molars have the selenodont character of other Pecora, the premolars are more adapted for cutting, with sharp edges.

The genus _Tragulus_ consists of several species (e.g. _T. stanleyanus_, _T. napu_, etc.), which have been aptly compared in external appearance to certain Rodents such as the Agoutis. The legs are delicate and slender, hardly "thicker than an ordinary cedar pencil." These creatures have got among the Malays a considerable reputation for astuteness, embodied in the saying, "Cunning as a _kanchil_." The male has tusks, which greatly contributed to the confusion of this creature with the totally different Musk Deer, _Moschus moschiferus_. It is even said to suspend itself by their aid to the branches of trees, and so avoid danger.

_Hyomoschus_ (or _Dorcatherium_ as it should properly be called) is West African. Its rich brown colour, with spots and stripes, is much like that of the Chevrotains, but it has shorter limbs. The only species is _D. aquaticum_, which is sometimes called, on account of its frequenting the banks of streams, the Water Chevrotain. Remains of this genus occur in Miocene and Pliocene strata of Europe.

The separate metacarpals, comparatively simple stomach, absence of horns, diffuse placenta, and spotted pelage are features which argue the primitive position of these animals among existing Artiodactyles.

Besides the two existing genera which have just been treated of, there are a number of extinct genera undoubtedly belonging to the same group.

_Gelocus_ (Eocene and Oligocene in range) is a European genus known from France. It differs from the living members of the group by the fact that the second and fifth toes on both hind- and fore-feet are represented, as in certain Deer, {284} by rudiments at the upper and at the lower end only; they are deficient in the middle. The middle large metacarpals, though closely applied, are not fused. The metatarsals, on the other hand, are, or are not fused, according to the species. A later form is the genus _Leptomeryx_ from the Miocene of North America. This genus departs from the typical Traguline structure in more than one point. The tympanic bulla is hollow instead of being filled with cancellated bone; the cuneiform is not fused with the cuboid and navicular, though the latter are with each other; the lateral digits of the hind-feet are rudimentary. The magnum and trapezoid, however, are fused. In the fore-feet the middle metacarpals are separate, and the lateral less perfect metacarpals have toes. The metatarsals are fused.

Not definitely referable to the Tragulidae, but coming near to them, are the PROTOCERATIDAE. Of this family there is but one well-known genus, _Protoceras_,[192] from the Miocene of North America.

The skull is singularly reminiscent of _Dinoceras_, with which this quite Artiodactyle genus has, of course, nothing to do. It merely exemplifies the phenomenon of "parallelism." In general form it is peculiarly long and low. There are three pairs of bony protuberances: one, the largest, pair are situated on the maxillae rising up just behind the implantation of the canine teeth; the parietals have a second pair; and a third much more diminutive pair of bosses are upon the frontals, near their junction with the nasals. This description refers to the male; the female has only traces of the parietal bosses. These were all possibly tipped or sheathed with horn or roughened skin. The dentition of this genus is precisely that of the Tragulidae, _i.e._ I 0/3 C 1/1 Pm 4/4 M 3/3. The orbit is completely encircled by bone; the auditory bulla is not swollen; the premaxillae are small.

The nasal cavity is very large and open, the end of the nasal bones anteriorly being situated at about the middle of the skull; this would seem to indicate at least a flexible and long nose like that of the Saiga Antelope, if not a trunk.

The brain was of good size, and quite well convoluted.

The limbs are constituted on the Traguline plan; in the fore-limbs the middle metacarpals are quite free from each other, and the more diminutive lateral digits are complete. The {285} metatarsals are free, but with a tendency to fusion; the lateral toes are only represented at the upper extremity. The carpal bones are separated.

This animal, which was about the size of a Sheep, though of more delicate proportions, was allied not only to the Tragulidae but to the Giraffidae; it is impossible to refer it definitely to either family.

B. TYLOPODA.

FAM. 5. CAMELIDAE.--This small group of Selenodonts includes only the Camels and Lamas. The limbs are long and have no traces of the second and fifth toes. The fused metacarpals and metatarsals diverge somewhat at their distal ends. In the upper jaw is a single pair of incisors. The stomach differs from that of the typical Ruminants. The rumen has smooth and not papillose walls, and from it are developed the "water cells," diverticula with narrow mouths provided with a closing sphincter muscle. The psalterium is reduced to a mere vestige, and so the stomach has, as in the Tragulina, but three chambers. This, so far ancient, character in the structure of the Camel tribe is associated with another, also seen in the more primitive Ungulates, viz. the diffuse character of the placenta. A very singular peculiarity of this group is the fact that the blood corpuscles instead of showing the ordinary mammalian round contours are elliptical.

FIG. 148.--Bactrian Camel. _Camelus bactrianus._ x 1/30.

The genus _Camelus_, confined to the Old World, is made up of two quite distinct species, the Bactrian Camel, _C. bactrianus_, with two humps, and the Dromedary, _C. dromedarius_, with only one. The former species is Asiatic. It is a singular fact that neither of the species is known to occur in a genuinely wild condition. The so-called "wild" Camels appear to be invariably feral. The two species will interbreed; and there is at the Zoological Society's Gardens such a hybrid, which has the general appearance and shaggy brown hair[193] of the Bactrian animal, but the one hump of the Dromedary. It may be that the Bactrian Camels of Lob-nor are really wild; but the desert contains so many remains of cities destroyed by sand-storms that these reputed wild {286} Camels may be the descendants of animals belonging to the inhabitants of those cities. A strayed herd of Camels has established itself in a feral state in Spain. Otherwise the genus does not occur in Europe. The Camels are also represented in the New World. The genus _Lama_ (_Auchenia_ of many authors) belongs to this family. These Camels differ from their allies in the Old World by their smaller size, by the absence of the characteristic hump, and by the dropping of one premolar, the dental formula being otherwise similar. A variety of names, Lama, Alpaca, Huanaco, Vicuna, have been applied to these animals; but it appears that the names are in excess of the number of the species. Mr. Thomas, who has lately inquired into the matter, will only allow two, the Huanaco, _Lama huanacos_, of which there are two domestic races, the Llama and the Alpaca, and the Vicuna, _Lama vicugna_. They are both South American in range. Not only is there a herd of escaped Camels in Spain, but the Spaniards attempted to introduce and acclimatise the useful Lama. The first Lama ever seen in Europe was brought in the year 1558 to {287} the town of Middelburg in Holland; it was purchased and presented to the Emperor of Germany. Gesner gives a curious figure of it, representing the animal as a comparatively colossal beast submitting itself to the guidance of a dwarfish man. The habit of "spitting" of the Lama is well known. Augustin de Zarate and Buffon speak of the Lama as having no protection save this habit, which is more than a mere ejection of saliva: the contents of the stomach are forcibly shot at the object of its annoyance. It can also kick and bite. In the intestines (as in those of some other mammals) are found Bezoar stones, or Bezards as they are variously spelt. These were once valued in medicine, and even so lately as 1847 were, according to Gay, the historian of Chili, in vogue; these concretions, comparable to the ambergris of the Whales, were supposed to be an antidote to poison.

FIG. 149.--Lama. _Lama huanacos._ x 1/12.

EXTINCT CAMELS.--The earliest cameloid type is the genus _Protylopus_,[194] of which we are acquainted with an imperfect skull {288} and the greater part of a radius and ulna belonging to one individual, and most portions of the hind-limbs in other specimens. The one species, _P. petersoni_, was about the size of a "jack rabbit," and is late Eocene (Uinta formation) and American in range. The teeth of this mammal are the typical forty-four, and the canines are not pronounced, being incisiform in shape. In the skull the nasals overhang, as in the genus _Poebrotherium_. The orbit is not closed by bone. There is in this ancient Camel a trace of the supra-orbital notch so characteristic of the Camel tribe. "The vertebrae resemble those of the modern Lamas closely in their general proportions." The lumbars have the usually Cameloid formula of 7. This genus has but two functional toes on the hind-feet, the second and fifth being reduced to vestiges. It is interesting to note that the radius and ulna appear to remain distinct, except in very old animals, in which they come to be co-ossified in the middle only, thus foreshadowing their complete union in the next genus, _Poebrotherium_. The present genus, moreover, as well as _Poebrotherium_, was distinctly unguligrade; it has not acquired the characteristic phalangigrade mode of progression of the modern types of Camels.

FIG. 150.--Skull of _Poebrotherium wilsoni_. _i_^1, _i_^2, _i_^3, Incisors 1-3. x 1/2. (After Wortman.)

The American and Oligocene _Poebrotherium_ has been recently and exhaustively studied by Professor Scott.[195] It was considerably smaller than a Lama. Its neck was long as compared with other Artiodactyles, but still shorter than that of the Lama. It was a lightly-built, graceful creature, with apparently some external likeness to a Lama. It is an important fact to notice that at this {289} period, and for a long time after, there were no types referable to the Camelidae in the Old World. Though a Camel in many features of its organisation, _Poebrotherium_ was "generalised" in many ways. Thus the metacarpals and metatarsals were not fused to form a cannon bone, and the two lateral digits were represented by splint rudiments of metacarpals and metatarsals. The dentition was complete. The skull though distinctly Tylopodan, also shows more generalised characters. Thus the orbit is not quite, though nearly, completed by bone. In the Camel it is quite closed. The nasal bones are much longer, reaching nearly to the end of the snout. The odontoid process of the axis vertebra is not spout-like as in existing forms, but cylindrical, though slightly flattened upon the upper surface. The scapula is described as being more like that of the Lama than of the Camel, though variations occur which approximate to the Camel. The brain, judging of course from casts, has those sulci "which are common to the whole series of Ungulates, and closely resemble those of a foetal Sheep."

FIG. 151.--Anterior surface of axis of Red Deer, x 2/3. _o_, Odontoid process; _pz_, posterior zygapophysis; _sn_, foramen for second spinal nerve. (From Flower's _Osteology_.)

Later in historical sequence than _Poebrotherium_, and structurally intermediate between it and _Protolabis_, is the Miocene genus _Gomphotherium_. It shows an advance in structure upon _Poebrotherium_, in that the orbit is completely encircled by bone, though the posterior wall is thin; the lower canines instead of being incisiform are curved back as in later Camels, and separated by a wide diastema from the preceding and the succeeding teeth.

Later in age than _Poebrotherium_ is _Protolabis_, a _Tylopod_ in which the full number of teeth is still retained; its skull presents no particular changes from the Poebrotherine type; the nasals, however, are somewhat shortened.

Later still in point of time is _Procamelus_. In this form we have apparently an ancestral stock, whence both Camels and Lamas were derived. The upper incisors are as in existing forms, but the first and second persist for a somewhat longer time. The skull shows two well-marked types of structure; in _P. occidentalis_ {290} there are more points of likeness to the Lama, in _P. angustidens_ to the Camel. In both, the orbits are completely encircled by bone. The nasals are much shortened. The odontoid process of the axis is still more concave than in _Poebrotherium_, but not spout-like as in existing forms. This fact shows that the spout-like character of the Camels' odontoid process is not a point of affinity to other Artiodactyles--in fact the occurrence of the same form of odontoid process in Perissodactyles is enough proof of this. We must come to the conclusion that the form is adaptive in all cases. If we were not obliged on palaeontological evidence to come to this conclusion, the structure in question is just one which would be fastened upon as evidence of genetic affinity; for it is a resemblance in a small though distinctive point of structure having no obvious relation to utility. The metacarpals and metatarsals have coalesced to form the cannon bones, though a rudiment of one metacarpal seems to remain. The genera referred to appear to be on the direct line of descent of the modern representatives of the family. But there are other forms which are offshoots of the main stem. Such are _Homocamelus_, _Eschatia_, and _Holomeniscus_. The last two are Pliocene and American; the teeth are much reduced.

C. PECORA.

The Pecora are a group which possess so many characters in common that it is not an easy task further to subdivide them.

In all there are but two functional digits on the feet, and the metacarpals and metatarsals of these are fused. There are no upper incisors, and canines in the upper jaw are not universal, and generally small. Horns are confined to this group of the Selenodontia.[196] The premolar teeth are of a simpler form than the molars. The stomach has four chambers, of which two may be regarded as belonging to its cardiac half and two to the pyloric. The former are, in the first place, a large paunch or rumen, followed by a smaller reticulum, so called on account of the network arrangement of the folds of its lining membrane. Connected with the latter, and constituting the first part of the pyloric half of the stomach, is the psalterium or "manyplies," so called on account of the longitudinal folds, like the leaves of a {291} book, into which its lining membrane is raised. Finally there is the abomasum, out of which proceeds the small intestine. Garrod has observed that the chamber of the stomach which varies most among the Pecora is the psalterium. This chamber is specially large in _Bos_, and particularly small in the Antelopes _Nannotragus_ and _Cephalophus_. But its variation relates more especially to the folds of its mucous membrane. These folds are of varying lengths and have a definite arrangement There may be as many as five sets of laminae of regular depths. The most simple psalterium is that of _Cephalophus_, where there are only two sets of laminae of different sizes, a deeper set and a very much shallower set; this form is termed by Garrod "duplicate." Most common is the "quadruplicate" arrangement, with four sets of laminae of differing depths. In all Pecora the liver is but little divided by fissures.

FAM. 6. CERVIDAE.--The Deer tribe is a very extensive one, and, with the exception of Africa and Australia, world-wide in distribution.[197]

The Deer are absolutely distinguished from all other Ruminant animals by the existence of antlers, which are invariably present in the male sex, save in the aberrant genera _Moschus_ and _Hydropotes_; in the Reindeer alone are antlers present in both sexes. The general characters of these appendages have been dealt with on a former page (p. 200), where they are compared to, or rather contrasted with, the horns of the Bovidae. These antlers, so characteristic of the Cervidae, are very variously developed among the members of the family. Thus in _Elaphodus_ the antlers are very small and entirely unbranched. In the Muntjacs, _Cervulus_, the antlers are hardly larger, but they have a small anterior branch arising from near the pedicel, the "brow tine." In _Cariacus antisiensis_ only one branch, the brow tine, is present, but it is nearly as long as the main stem of the antler, the "beam." In _Capreolus capraea_ the beam bears two tines; in _Cervus sika_ three; in _C. duvauceli_ two of the three tines present bear secondary branches. There are other complications (some of which are illustrated in Figs. 152-157) of the simple antler which culminate in the complex antlers with their expanded "palms" of the Elk and the Fallow Deer. {292}

Another highly-interesting fact concerning these same antlers is their gradual increase in complexity of tines and palm from the Miocene _Cervus matheroni_ to the great Irish Elk of post-Tertiary times.

Beyond the antlers there seems to be no character of universal applicability which distinguishes the Cervidae from the nearly-related Antelopes. There are, however, a number of structural features which are _nearly_ universally characteristic. Excepting _Moschus_ (which Professor Garrod would not allow to be a "Deer"), no Cervine has a gall-bladder[198] to its liver. All Bovidae (including Antelopes) have, with the exception of _Cephalophus_.

A small but constant character of the Deer is the existence of two orifices to the lachrymal duct. The genus _Tragelaphus_ alone among Antelopes shows this character.

So far as is known the placenta of the Deer has but few cotyledons, that of the Bovidae many. But not many types are known.

The navicular, cuboid and ectocuneiform are often united. This is never the case in the Bovidae.

The first and second phalanges of the lateral (imperfectly developed) digits are always present except in the Muntjacs; they are never found in Bovidae. The Deer always present a light brown to a darker brown coloration. _Elaphodus michianus_ is almost black. There is commonly white on the under parts and beneath the short tail. Some Deer, such as the Fallow Deer, are spotted; and the young of others that are uniformly coloured when adult are spotted. In some cases a winter coat, darker than the summer coat, is developed.

Altogether some sixty species of Deer are known, of which the preponderance are Old-World forms. The Deer of the Old World are distributed among the genera[199] _Cervus_ (all Europe and Asia); _Cervulus_, the Muntjacs (India, Burmah, China, etc.); _Hydropotes_ (Eastern China); _Capreolus_ (Europe and Central Asia); _Elaphodus_ (Eastern China); there is one American _Cervus_, the Wapiti. The American genera are _Cariacus_ and _Pudua_. The Elk (_Alces_) and the Reindeer (_Rangifer_) are circumpolar. The principal structural modification which occurs within {293} the family Cervidae concerns the rudimentary fifth and second toes. In _Capreolus_, _Hydropotes_, _Moschus_, _Alces_, _Rangifer_, and _Pudua_ there are considerable remains of the lower parts of metacarpals II. and V.; in the other genera smaller traces of the upper ends of the same bones.

The two most abnormal genera are _Moschus_ and _Hydropotes_, more particularly the former, which neither Sir V. Brooke nor Professor Garrod allow to be members of the family at all. _Moschus_ is usually placed in a special sub-family by itself, Moschinae, the remaining Deer being referred to another sub-family, Cervinae.

SUB-FAM. 1. CERVINAE.--The genus _Cervus_ comprises rather over twenty existing species, which, except the Wapiti (_C. canadensis_), are exclusively Old World in distribution. The principal features of variation in the genus, in accordance with which it has been divided up into sub-genera, are (1) palmated (Fallow Deer, _Dama_) or non-palmated antlers; (2) adults spotted with white at all ages and seasons (_Axis_), or in summer only (_Pseudaxis_), or not at all; (3) spotted or unspotted young; (4) existence or absence of rudimentary canines in the upper jaw.

Among the members of this genus, _Cervus (Elaphurus) davidianus_ is interesting as having been first observed by the missionary Pere David in a park belonging to the Emperor of China near Pekin. Its horns are remarkable for dividing early into two branches of equal length, of which the anterior again branches into two. Specimens of this Deer were ultimately obtained for the Zoological Society's Gardens.

The species of _Cervus_ are fairly distributed between the Palaearctic and the Indian regions. The Palaearctic species, such as Luehdorff's Deer (Fig. 152), are mainly Asiatic. _Cervus elaphus_ and _Cervus dama_ alone are European and British. The former of course is the Red Deer, the latter the Fallow Deer. The Red Deer is reddish-brown in summer and greyish-brown in winter, with the white patch on the rump so common in the Deer tribe. The Red Deer is genuinely wild in Scotland, in certain parts of Devonshire and Westmoreland, and in the New Forest. At the beginning of the last century, according to Gilbert White, there were 500 head of deer in Wolmer Forest, which were inspected by Queen Anne. The antlers may have as many as forty-eight points; and a stag with more than the three anterior tines is termed a "Royal Hart." The Fallow Deer has {294} palmated antlers, and is usually spotted. It seems to be an introduced species, common report pointing to the Romans as the introducers. It would be more correct to say "re-introduced," for fossil remains of this Deer have been met with.

FIG. 152.--Luehdorff's Deer. _Cervus luehdorffi._ x 1/15. (From _Nature_.)

_Elaphodus_[200] contains probably two species, _E. cephalophus_ of Milne-Edwards and _E michianus_ of Swinhoe, both from China. The antlers are small and unbranched; the canines in the male are massive; it differs from _Cervulus_, to which it is closely allied, principally in the absence of frontal glands. The second {295} species has a dark iron-grey pelage, and the late Mr. Consul Swinhoe described it as very Goat-like in aspect.

_Capreolus._--The Roe Deer has fairly complex antlers. It is a small Deer and has spotted young. The common Roe Deer, _C. capraea_, is a native of this country. It is the smallest of our Deer, and its antlers only have three tines in stags of the third year. It is a singular fact about this Deer that though the pairing season is in July and August, the young are not born until the following May or June, a period which does not represent that of gestation. The germ remains dormant for some time before developing.

FIG. 153.--Mule Deer. _Cariacus macrotis._ x 1/15. (From _Nature_.)

The Muntjacs, _Cervulus_, form a distinct generic type confined to the Indian and the South-Eastern Palaearctic region. They are small Deer with spotted young, and short one-branched antlers placed upon pedicels as long as themselves. The canines are strongly developed in the males. There are about half-a-dozen species.

_Cariacus_ is exclusively American in range, and contains about twenty species. There are or are not upper canines. The young {296} are spotted. The antlers are occasionally very simple; in _C. rufus_ and a few allies (placed in a special sub-genus _Coassus_) they are simple spikes without branches. In this genus, and in the nearly allied and also New-World _Pudua_, the vomer is prolonged backwards and divides the posterior nares into two. The bulk of the species are South American.

FIG. 154.--Chilian Deer. _Cariacus chilensis._ x 1/12. (From _Nature_.)

_Pudua_, just mentioned, comes from the Chilian Andes. It is a small Deer without canines and with minute antlers. Other generic names have been proposed for various species of American deer.

_Hydropotes inermis_ is a small perfectly hornless Deer, living on the islands of the Yang-tse-kiang. The male has tusks; the young are spotted. Though, like other deer, _Hydropotes_ has no gall-bladder, both Mr. Garrod[201] and Mr. Forbes[202] found the {297} rudiments of one in the shape of a white ligamentous cord. Mr. Forbes has especially dwelt upon the likeness of the brain to that of _Capreolus_. The female has four teats, and produces three to six young at a time.

FIG. 155.--Water Deer. _Hydropotes inermis._ x 1/10. (From _Nature_.)

_Alces machlis_, the Elk or Moose, is a circumpolar species with palmated antlers and is of large size. The young are unspotted. This animal is the largest of the Deer tribe. The aspect of this creature is by no means that of a Deer, the long, thick, and rather prehensile upper lip not by any means suggesting the family to which it belongs; the legs, too, are ungainly through their unusual length. The Moose has a curious method of protecting himself from Wolves. Instead of moving about during heavy snowstorms, and being thus on the heavy ground an easy prey for these agile enemies, the animal forms what is known as a "Moose yard." An area of ground is kept well {298} trampled down, and the animal contents itself with browsing upon the adjacent stems. The well-trampled ground gives an easy footing, and by his powerful horns the great stag is able to keep his enemies at bay.

FIG. 156.--Moose. _Alces machlis._ x 1/20.

_Rangifer tarandus_, the Reindeer, is unique among Deer by reason of the fact that both sexes wear antlers. These antlers are palmated. The brow tine and the next or bez tine are also palmated and are directed forwards and a little downwards. The young are unspotted. The pelage alters in winter. Like the Moose, the Reindeer is circumpolar. As is well known, during the Pleistocene period the Reindeer extended its range as far as the South of France. Even in the historic period it is said to have been hunted in Caithness.

Reindeer, like so many other particularly Arctic animals, have regular migrations. In Spitzbergen, for instance, the animal migrates in the summer to the inland region of the island, and in {299} the autumn back again to the sea coast to browse upon the seaweed. These migrating herds have been stated to be led by a large female.

FIG. 157.--Reindeer. _Rangifer tarandus._ x 1/15.

SUB-FAM. 2. MOSCHINAE.--_Moschus moschiferus_[203] is a native of the Asiatic Highlands. It is 3 feet or so high, perfectly hornless, and with very large canines in the male. It is noteworthy that in _Hydropotes_, where the canines are also very large, horns are absent. These are examples, perhaps, of correlation. The musk sac (whence the name) is present on the abdomen of the male only. There is no crumen or suborbital gland, which is so generally (though by no means universally) present in Cervidae. But the male has, in addition to the musk glands, glands near the tail and on the outside of the thigh. Unlike other Deer, the lachrymal bone of _Moschus_ bears but one orifice. The feet, so far as concerns the preservation of the outer rudimentary {300} metacarpals, are of the more ancient type represented in _Alces_, _Hydropotes_, etc. A gall-bladder is present. The young, as in so many Cervidae are spotted; but the adult is of a greyish-brown colour.

FIG. 158.--Musk Deer. _Moschus moschiferus._ x 1/6. (From _Nature_.)

There is no doubt that _Moschus_ is more nearly related to the Cervidae than to any other Ruminants. It is regarded by Sir W. Flower as "an undeveloped deer--an animal which in most points (absence of horns, smooth brain, retention of gall-bladder, etc.) has ceased to progress with the rest of the group, while in some few (musk gland, mobile feet) it has taken a special line of advance of its own."

The musk itself, which gives its name to the creature, is found in a gland on the belly, about the size of a hen's egg. The whole gland is cut out and sold in this condition. Such quantities of musk deer have been and are killed for this purpose that the rarity of the animal is increasing. In the seventeenth {301} century it was so common that the traveller Tavernier purchased 7673 musk "pods" in one journey, or, according to Buffon, 1663. The tusks, which recall those of _Hydropotes_, to which _Moschus_ is not nearly allied, and of _Tragulus_, with which it has of course still less connexion, are said to be used for the digging up of roots. Its feet, in relation to its mountain-ranging habits, are very mobile.

EXTINCT SPECIES OF DEER.--It has been already mentioned that the most primitive kinds of Deer had no horns at all, resembling in this the modern _Moschus_ and _Hydropotes_, and that with lapse of time went hand in hand an increasing complexity of antler; the facts of palaeontology harmonising in the most striking manner with the facts of individual development from year to year. The oldest forms seem to be more nearly akin to the living Muntjacs, and their remains occur in the lowest Miocene beds of both Europe and America. At present the group is confined to the warmer parts of Asia and some of the islands belonging to that continent.

One of the oldest types is _Amphitragulus_. This genus, which consists of several species, inhabited Europe, and differed from living Muntjacs in being totally hornless in both sexes; the skull had no lachrymal fossa or deficient lateral ossification.

Nearly allied is _Dremotherium_ of similar age and range.

The Middle Miocene has furnished the remains of the genus _Dicroceras_. This is the earliest Deer in which horns have been found. The horns are, as the name of the genus implies, bifid, and have, like those of the living Muntjac, a very long pedicel. This is also a European genus like the last. From this period we come across true Deer, which commence in the Upper Miocene and have branched horns. Moreover they belong, at least for the most part, to the existing genera. One of the most remarkable forms is _Cervus sedgwicki_ (sometimes placed in a separate genus, _Polycladus_) from the Forest Bed of Norfolk and from the Upper Pliocene of the Val d'Arno. This creature was remarkable for its multitudinously-branched antlers. These end in no less than twelve points. No Deer exists or has existed in which the horns are so completely branched. They are like those of a Red Deer exaggerated.

FIG. 159.--Giraffe. _Giraffa camelopardalis._ x 1/40.