Fig. 137.
Fig.137.—Three figures showing the cranial evolution ofTitanotherium. Upper figure,T. trigonoceras; middle figure,T. elatum; lower figure,T. platyceras. (After Osborn.)
The genus further agrees with the Artiodactyles in the structure of the carpus. The toes of the fore-limb are four, those of the hind-limb three; but while the hind-limb is undoubtedly Perissodactyle in the arrangement of its component parts, the fore-limb shows a hint of an Artiodactyle mode of structure. This limb is paraxonic, the axis of the limb passing between the two middle digits. It may be that this genus represents more nearly than any other Perissodactyle or Artiodactyle the primitive stem from which both have diverged, though, of course, it is not old enough to be very near to the actual ancestor. The molar dentition is the typical one; the incisors seem to vary as to their presence or absence, and, if present, in their numbers. In comparing the older with the more recent forms it is noteworthy that there has been an increase of size exactly as there has been during the evolution of the Camels and some other groups of Ungulates. As already mentioned, the size of the horn cores also increases until it culminates in the extraordinary species,T. platycerasandT. ramosum, in which these are half as long as the skull, flattened in form, and connected at their bases by a "web" of bone. Arrived at this amount of specialisation the genusTitanotheriumapparently exhausted its capacities for modification and ceased to be. The many generic names may be explained by sexual differences on the one hand and an incomplete knowledge of connecting links on the other.[168]
Palaeosyopsis somewhat like a Tapir in build, the skull especially resembling that of the Tapir. As inTitanotheriumthe molar teeth, instead of having an outer wall formed by fused cusps, have aW-shaped outer wall on one side and two or one cusps on the opposite side. It is, moreover, an Eocene form, and in correspondence with its greater age is more primitive in some points of structure, for example, in the absence of horns and in the full dental formula. The fore-limbs are four-toed, the hindthree-toed. It was intermediate between a Tapir and a Rhinoceros in size. It has been shown, too, from casts of the interior of the skull, that the cerebral hemispheres are much less convoluted than were those ofTitanotherium.
Related toPalaeosyopsis another primitive Titanothere, the genusTelmatotherium. This is also Eocene, from the Uinta Basin, the uppermost of Eocene strata. The skull of these creatures was rather elongated, and not unlike that of a Titanothere in general aspect. The dentition was complete and the canines not very large. The horns, which acquire so prodigious a development in the later Titanotheres, are just recognisable in at any rate many species of this genusTelmatotherium, the name being thus by no means an apt one. Better was that proposed by Dr. Wortman, ofManteocerasor "prophet horned." The horns are small elevations upon the frontals just at the junction of these with the nasals, and, indeed, lying partly upon the latter bones. InT. cornutumthe horns are chiefly borne upon the very long nasals, whose size contrasts with the same bones in the more highly-developedTitanotherium. It appears to be quite possible thatTitanotheriumwas evolved from the genusTelmatotherium.[169]
Whether theMacraucheniidaeshould be considered as a separate group of Ungulata is a matter of dispute. Cope placed them in a special order of Ungulates which he called Litopterna. Zittel, on the other hand, regards them as definitely Perissodactyles. One curious point of resemblance to existing Horses is shown—that is the presence of a pit in the incisor teeth. This matter seems to be so important as to need a placing of these forms in the neighbourhood of the Perissodactyles, even of the Equidae; it is so peculiar a character, and apparently so little related to any obvious similarity in way of life, that it seems to mark a special affinity. Not so the fact that inMacraucheniaat any rate the orbit was entirely surrounded by bone as in the Horse. We find that condition so frequently acquired in many groups,—a development from an earlier condition where the cavity for the lodgment of the eye is in continuity with the temporalfossa, that it cannot be regarded as anything more than a mark of specialisation. It is, in fact, the case that the Macraucheniidae are in many points specialised, while retaining many primitive features of structure.
The chief primitive features are: the non-alternating positions of the wrist- and ankle-bones; these, of course, interlock in the Perissodactyles of to-day and in many extinct families. Then the absence of a diastema in the tooth series, coupled with the presence inMacraucheniaof a complete dentition. The small brain may be referred to the same category.Macraucheniamust have been a strange-looking animal. It walked upon three toes on each limb; the skull was Horse-like in general form, but the nostrils are removed to a point about as far back as in the Whales or nearly so, the nasal bones being correspondingly reduced. This it is thought argues a proboscis. The humerus is particularly compared by Burmeister[170]to that of a Horse. The radius and ulna though both well developed are fused. The neck is long, and, as in the Camel, the vertebral arteries run inside the neural arches. Since the fore-legs seem to have been rather longer than the hind-legs, though only very slightly, and the neck was long, the animal may have presented some likeness to the Giraffe. It is interesting to note that in the proportions of humerus to ulna this animal is more Lama-like than Horse-like. On the other hand, the proportions of femur to tibia are more Horse-like. The remains of the creature are limited to South America, and to quite superficial deposits. It is evidently a specialised type, and has pursued a course parallel to that of the Horse. Much nearer to the Horse however, but apparently by convergence only, is the genusThoatherium, usually placed in a separate family, theProtorotheriidae. In this creature, which has many archaic characters, the toes are reduced to one in each foot. In an allied form,Protorotherium, we have the two lateral toes diminishing just as inAnchitherium.
Fig. 138.
Fig.138.—Bones of the Manus—A, of Pig (Sus scrofa). × ⅓.B, of Red Deer (Cervus elaphus). × ½.C, of Camel (Camelus bactrianus). × ⅛.c, Cuneiform;l, lunar;m, magnum;m2,m5, second and fifth metacarpals;R, radius;s, scaphoid;td, trapezoid;u, unciform;U, ulna;II-V, second to fifth fingers. (From Flower'sOsteology.)
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 salientof 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."[171]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 coursethe 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 inOreodon, 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.
Fig.139.—Dorsal surface of right tarsus of Red Deer (Cervus elaphus). × ⅓.a, Astragalus;c, calcaneum;c3, cuneiform;cb, cuboid;mIII,mIV, metatarsals;n, navicular. (From Flower'sOsteology.)
The carpal bones of the Artiodactyla alternate in their articulation; the primitive state of affairs[172]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. Onecan see how this may be purely adaptive, the push of the hind-legs in running needing a firmer support. InHyomoschusthis 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.[173]The number of ribs varies from twelve (Camelus,Hydropotes) through thirteen (Cervus,Gazella) to fourteen inDicotyles,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-knownPantolestes); 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 inTragulus, and four in the typical Ruminants such asCervus,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 speciesin 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 genusPotamochoerus.[174]
Fam. 1. Hippopotamidae.—The family Hippopotamidae contains of existing genera onlyHippopotamus, 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[175]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 eachjaw, and they were distinguished as a genusHexaprotodon, contrasting withTetraprotodon, 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.
Fig.140.—Hippopotamus.Hippopotamus amphibius.×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.[176]
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 itcan 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.
Fig.141.—Wild Boar.Sus scrofa.×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 inBabirusa. They are generally hairy, but the Babyroussa is an exception, whilePhacochoerusis 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 inDicotyles) there is a caecum. The kidneys are smooth, and the liver is more lobate than inHippopotamus. 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[177]is complete. A single species, the so-calledS. 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" ofSushave been described, but Dr. ForsythMajor is disposed to reduce them to four if not to fewer species. He allows the widely-rangingS. scrofa,S. vittatus, and the eastern MalayanS. verrucosusandS. barbatus.
Fig. 142.
Fig.142.—Pygmy Hog (fromNature).Sus salvania.×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 termedPorcula salvania.[178]The Wild Boar of Europe isSus 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 Boarin this country down to so late a period as the end of the sixteenth century.
Fig. 143.
Fig.143.—Wart Hog.Phacochoerus aethiopicus.×1⁄6.
The African Wart Hog, genusPhacochoerus, 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 genusSusby 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. aethiopicusandP. 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.
Fig.144.—Head of Wart Hog.
The Celebesian Babyroussa, genusBabirusa, is an almost hairless hog with enormously upturned tusks in both jaws of themale. In the Wild Boar there is a hint of this, which is carried still further inPhacochoerus; but inBabirusathe 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.
FromSusproper the African and MalagasyPotamochoerus, 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 JavanSus verrucosusshows 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[179]recognises five species, of which only one is from Madagascar.
Fig. 145.
Fig.145.—Peccary.Dicotyles tajaçu.×1⁄6.
Fam. 3. Dicotylidae.—The Peccaries are generally placed in a different family from that of the other Pigs. This family,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.Susitself 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.Dicotylesoccurs in the Pleistocene of both North and South America, the regions which it inhabits at the present day. The genusListriodon, 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[180]occurs chiefly in the Miocene of both North America and Europe; butE. uintenseis Eocene. The orbits are completely encircled by bone in the more modern forms; this is not the case in the last-described genus, with whichE. uintenseagrees. The skull is also longer and more Pig-like. The zygomatic arch is powerful, with sometimes a large descending process, such as is found inDiprotodon, more faintly in Kangaroos, and in Sloths and certain extinct Edentates. The lower jaw has a pairof dependent processes near the symphysis, which suggest processes occupying a corresponding position inDinoceras. 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. PerhapsE. uintenseshould be separated as a distinct genus,Protelotherium.[181]
Hyotherium(which is regarded as identical withPalaeochoerus) 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 inTriconodonamong 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 genusChoeropotamushas 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 MioceneChaenohyushas lost the corresponding teeth of the upper jaw.
Homacodon[182]is a genus consisting of several species, which has a bunodont and complete dentition. The molars are sextubercular in the upper jaw.H. vaganswas 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.
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 incisorsin 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 AfricanHyomoschus. 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.
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.
As the Tragulina are undoubtedly the most ancient of the Selenodontia it will be logical to commence with an account of them.
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.
Fig.147.—Indian Chevrotain.Tragulus meminna.× ¼.
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 inTragulus(though separate inHyomoschus) they are a stage further than are the Pigs, in the direction of the typical Ruminants.
The stomach is comparatively simple, thus offeringintermediate 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[183]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 genusTragulusconsists 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 akanchil." 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(orDorcatheriumas 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 isD. 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,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 genusLeptomeryxfrom 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 theProtoceratidae. Of this family there is but one well-known genus,Protoceras,[184]from the Miocene of North America.
The skull is singularly reminiscent ofDinoceras, 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. Themetatarsals 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.
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.
Fig.148.—Bactrian Camel.Camelus bactrianus.×1⁄30.
The genusCamelus, 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[185]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 wildCamels 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 genusLama(Aucheniaof 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, Vicuña, 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 Vicuña,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 tothe 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.