Fig. 161.
Fig.161.—Loder's Gazelle.Gazella loderi.×1⁄10.
The Gazelles, genusGazella, are fairly numerous in species, which are both Palaearctic and Ethiopian. There are altogether twenty-five of them. The genus as a whole is characterised by the small or moderate size, the sandy coloration with white belly, the presence of dark and light stripes on the face and on the flanks. These streaks, however, are not always present, and their presence or absence serves to differentiate some of the species. The horns are usually present in both sexes. The horns are of fair length, ringed, and of lyrate form.
The Springbok is separated from the rest of the Gazelles, to which genus it is clearly most nearly related, as a genusAntidorcas. This genus differs fromGazellaby having only two lower premolars as inSaiga. Otherwise it resembles the Gazelles; there is but a single species,A. euchore, which is African.
Ammodorcasis closely allied to the Gazelles, but differs from them in having an elongated neck and also a long tail.A. clarkei, the only species, is limited to Somaliland.
Lithocranius, not unlike the last, has a still longer neck, which makes it almost Giraffe-like; its tail, however, is short. The scientific name is derived from the "solid stony character of the cranium." In running, this Gazelle carries the head forward in a straight line with the body. It is African.
Dorcotraguswith one species,D. megalotis, is a pigmy Gazelle restricted to Somaliland. Its likeness, on account of size and in some other superficial features, to the Klipspringer, led to its original confusion with that genus (Oreotragus).
Fig. 162.
Fig.162.—Sable Antelope.Hippotragus niger.×1⁄20. The horns of the specimen figured have not nearly reached their full dimensions.
A sub-family Hippotraginae, or Hippotragine section, includes a number of Antelopes which agree in the possession of four mammae, and of molars more like those of the true Oxen, ofhorns of some length, present in both sexes, and of a longish tail. They are all African in range.
The type genusHippotragushas its horns placed above the orbits; they are not twisted, but curved backwards. There are three species in the genus. Of these the best known isH. niger, the beautiful Sable Antelope. Its general colour is a rich, dark, glossy brown with white stripes on the face, and with a white belly. The other species are the Roan Antelope,H. equinus, and the Blaaubok,H. leucophaeus, of which the last specimen was probably killed in 1799.[205]
Fig. 163.
Fig.163.—Beatrix Antelope.Oryx beatrix.×1⁄16. (FromNature.)
The genusOryx(chiefly African, but also Arabian and Syrian) also contains a number of species, which are fairly familiar through the fact that several of them are always on view in the Zoological Society's Gardens. The genus differs fromHippotragusin that the horns, present in both sexes, are placed behind the orbits, and slant backwards in a line with the face. They are annulated. The Leucoryx (O. leucoryx) is of a pale colour, butthis is not so marked as inO. beatrix, which is largely white with, however, brown legs. The Gemsbok is a handsome creature with greyish tawny colour, much darker on the legs, and with a Gazelle-like, dark, side stripe. It has received its vernacular name on account of its supposed likeness to the Chamois ("Gemse"), just as the Rehbok was so-called from its supposed likeness to the Roe Deer, and the Eland to the Elk. The Beisa (O. beisa) is of a similar tawny colour to the last, and also with darker stripes.
The Addax (Addax) of North Africa, Arabia and Syria, has but one species (A. nasomaculatus). The horns are spirally twisted.
Fig. 164.
Fig.164.—Speke's Antelope.Tragelaphus spekii(♀). ×1⁄16.
The Tragelaphine section includes the Kudus, Elands, Nilgais, and Harnessed Antelopes. They are all long-horned (when the horns are present in both sexes), the horns being twisted; the nose is naked with a slight median groove, and all are Ethiopian or Oriental in range.
The genusTragelaphusincludes the Harnessed Antelopes, so called on account of the direction of the stripes suggesting harness. The females are hornless, and the colours of the two sexes are different. The hoofs are long and the toes rather unusually separable, which state of affairs is in accord with theswampy country affected by many.T. gratusandT. spekeiare larger forms; the Boschbok,T. sylvaticus, is smaller.
The Kudus, genusStrepsiceros, have more markedly twisted horns, which are absent in the female. The body is vertically striped with white. The largest species isS. kudu; a smaller form,S. imberbis, is from Somaliland.
Fig. 165.
Fig.165.—Eland.Orias canna.×1⁄25.
The last genus of this section or sub-family is the African Eland, genusOreas[206](which it appears should be speltOrias). The Elands are perhaps more Ox-like in appearance than the other members of this group, and in both sexes have horns, in which the spiral twisting is more close.Orias cannais the name of the common Eland.O. livingstoniihas been applied to an East African variety, which has thin and faint lateral stripes like the other members of the group to which it belongs.
The genusBoselaphusincludes onlyB. tragocamelus, the Nilgai, which is purely Indian in range. The female is hornless, and the horns of the male are smooth and not long.
The members of the Bovine section or Oxen are to be distinguished from other hollow-horned Ruminants by their stouter build and by the fact that the horns stand out from the sides of the skull and are simply curved, not twisted; and smooth, not annulate like those of other Ruminants. The muffle is naked, broad, and moist. The Oxen are widely distributed; but are entirely absent from the Australian region and from South America and Madagascar.
The true Oxen are perhaps best considered to form but a single genus,Bos. They have, however, been divided into a number of genera. Even the supposed aberrantAnoa depressicornisof Celebes hardly differs sufficiently to warrant its separation. In favour of this view, too, is the extraordinary ease with which different "genera" will cross with each other and produce fertile offspring. The following is the pedigree of an animal lately living in the Zoological Society's Gardens. The female offspring of a male Zebu and a female Gayal was mated with a male Bison. The female calf was again mated with a Bison and produced a calf, also a female, which contained therefore the three species,Bos indicus,Bibos frontalis, andBison americanus. It is clearly unwise in view of this fact to insist too much upon generic distinctions in any of those types.[207]
Of this genus the Oriental Gaur (Bos gaurus), the Gayal (B. frontalis), and the Banteng (B. sondaicus) form a well-marked section, characterised by their dark coloration and by the somewhat flattened horns.
The Gaur,Bos gaurus, has a more concave forehead than its allies; the horns are less curved than those of the Banteng, and less so than the horns of the Gayal (Bos frontalis). It inhabits the Indian Peninsula; and extends through Burmah to the extremity of the Malay Peninsula. The Malay name of this animal is Sakiutan, which simply means wild cattle. It chiefly frequents wooded hills and is an excellent mountain climber.
Bos frontalis, the Indian Gayal, has a white caudal disc like the last species, but the forehead is flat and the horns curve but little. It is chiefly known as a tame animal, and its occurrence in the wild state has been doubted. It has furthermore been suggested that it is merely a tame race of the Gaur alteredslightly through domestication. It is, however, said not to cross in a state of nature with the Gaur.[208]
Fig. 166.
Fig.166.—Gayal.Bos frontalis.×1⁄20.
The Banteng,B. sondaicus, is distributed through Chittagong, Tenasserim, and the Malay Peninsula to Java and Borneo. There are apparently two races of this animal. The species differs from the others by the fact that the horns are smaller and more curved; there is a white caudal disc; the forehead is narrower and the skull longer than in the others.
The American Bison and the European Aurochs form another section; they are indeed extremely alike, specific differences being hardly recognisable. The Bison of America, formerly present in such numbers that the prairies were black with countless herds, has now diminished to about a thousand head.
One of the largest of existing Bovidae is the Aurochs, Wisent, or European Bison,Bos bonasus(orBison europaeus). It is exceedingly like its American relative. Formerly the animal was much more widely spread than it is now, extending its range from Europe into North America. It is now limited to certain districts on the Urals, in the Caucasus, and a herd of them are kept up through the fostering care of the Emperor of Russia in the forest of Bielovege in Lithuania. The term "Aurochs" should not really be applied to this species but to the Wild Cattle,Bos taurus. It is, however, so generally used for the Wisent (which is the German name) that itis not necessary to change it. The Sclavonic name is Zubr or Suber. It is a great beast, standing 6 feet or so in height at the shoulder. It ranged further over Europe well within the historic period. In the days of Charlemagne it was spread over Germany and was a beast of the chase. In the year 1848 the Emperor of Russia presented a pair of these Oxen to the Zoological Society of London. At the time of their presentation an interesting communication was made to the Society by M. Dolmatoff, on the method of the capture of these two examples. The creature is not easy to capture and is alarming to confront. "The eyes," says an old writer, "are red and fiery; the looks are furious and commanding." It has of course the shaggy mane and hump of the American animal. The herd in Lithuania was said to be 1900 in the year 1856. Mr. E. N. Buxton,[209]who has lately visited the forest, quotes M. Neverli to the effect that at present the numbers are not more than 700.
Fig. 167.
Fig.167.—Bison.Bison americanus.×1⁄25.
Allied to this animal, and apparently still nearer to the American Bison, is the extinctB. priscusof Europe. The Pleistocene Bisons of North America,B. antiquusandB. latifrons, are not remote from the living forms. Finally, the MioceneB. sivalensisfrom India, and the PlioceneB. feroxandB. alleniof North America, take back this group to as remote a period as any other genus of Oxen.
Fig. 168.
Fig.168.—Yak.Bos grunniens.×1⁄15.
Fig. 169.
Fig.169.—British Wild Ox.Bos taurus.From Vaynol Park, Bangor. ×1⁄20.
The Yak,Bos grunniens, is a long-haired peculiar type, confined to the Thibetan plateau.B.(Anoa)depressicornisof Celebes is characterised by its straight horns; allied to it isB. mindorensis(Philippine Islands), supposed, however, to be a hybrid betweenit and some other species. Africa has at least two Buffaloes. We may finally mention the Wild Ox of Europe,B. primigenius, the supposed progenitor of our domestic cattle, believed to be still surviving in the herds at Chillingham, Chartley, and elsewhere. This animal is sometimes called the Aurochs. The Romans spoke of it as the Urus, and it appears to have formerly attained to more gigantic proportions than at present. It is the small size of the present race that is the chief objection to tracing them back to the large Oxen existing near London in 1174, and found sub-fossil in the Cambridgeshire fens.
Fig. 170.
Fig.170.—Punjab Wild Sheep.Ovis vignei.×1⁄10.
Of the true sheep, genusOvis, there are a considerable number of species. The Sheep are to be distinguished from the Goats by their rather stouter build and by the absence of the beard in the male. The horns are developed in both sexes, and are usually twisted and often of large size.
The Sheep are almost entirely Palaearctic and Nearctic. They only just get into the Oriental region. One of the finest species is the great Pamir Sheep,O. poli, whose length reaches 6 feet7 inches, and height 3 feet 10 inches. The horns of this fine Sheep may measure more than five feet round the curves. The Rocky Mountain Bighorn (O. montana) is a Sheep ranging along the Rockies as far south as New Mexico, and also to the far north; they are not confined to the chain of mountains mentioned, but occur also on the mountains of British Columbia down to those of California. The horns are not quite as large as those of the last species, but measurements give a length (along the curve) of 32 to 40 inches.
Fig. 171.
Fig.171.—Himalayan Burrhel Sheep.Ovis burrhel.×1⁄12. (FromNature.)
Fig. 172.
Fig.172.—Blanford's Sheep.Ovis blanfordi.×1⁄10. (FromNature.)
Just as the Goats are often limited to islands and small stretches of country, so are the Sheep. Thus Cyprus has a species,O. ophion, peculiar to itself. This, which is known as the Cyprus Mouflon, is limited to a range of mountains, the Troodos, in that island. In 1878 it was believed that the animal was nearly exterminated, a flock of twenty-five members alone surviving. They have, however, since increased. Confinedto the Thibetan plateau areO. hodgsoniandO. nahura. Corsica has the Mouflon,O. musimon; and the Barbary Sheep or Arui,O. tragelaphus, is found only in Northern Africa.Ovis burrhelandO. blanfordiare Indian forms.
Fig. 173.
Fig.173.—Barbary Sheep.Ovis tragelaphus.×1⁄10.
Fig. 174.
Fig.174.—Thar.Capra jemlaica.×1⁄10. (FromNature.)
Ovis nahurais chiefly responsible for the impossibility of strictly separating the Sheep and Goats. It has no suborbital glands or lachrymal fossae, which are as a rule present in the Sheep and absent from the Goats. On the other hand interdigital glands are present, which is the case with Sheep. Its habits, too, are a blending of those of the Sheep and the Goat. It lives largely on undulating ground like Sheep, and frequently lies down during the day on its feeding ground. On the other hand it is, like the Goats, a splendid climber.
The Goats, genusCapra, differ from the Sheep in their slighter build and in the fact that the horns are not spirally curved, but arched over the back. There is also the characteristic beard,and the male is odorous. The true Goats are almost exclusively Palaearctic in range. They show the limited distribution of the Sheep, a distribution which follows from their mountain-loving habits.
Fig. 175.
Fig.175.—Sinaitic Ibex.Capra sinaitica.×1⁄10.
Thus we have the Spanish Ibex (C. pyrenaica), limited to the Pyrenees and other mountain ranges of the peninsula;C. ibex, the Steinbok of the Alps and the Tyrol; the Markhoor,C. falconeri, of certain mountain ranges of Afghanistan; the Caucasian, Sinaitic, and Cretan Ibexes, and the Thar.
Capra aegagrus, the Persian Wild Goat, ranges from the Caucasus to Sind. It is this animal which produces the true "bezoar stone." The substance in question is a secretion apparently found in the stomach. It is still, according to Mr. Blanford, regarded as an antidote to poison in Persia. Buffon called this Goat the "Pasan," which is evidently a corruption of the word bezoar. When the substance was in repute as a medicine of the "alexipharmic" kind, the supply naturally came up to the demand. Thus the bezoar stones of the Lama in South America gained repute, and there were "Oriental bezoar, cowbezoar, hog bezoar, and monkey bezoar"! As concretions of one kind or another are not uncommon objects in the alimentary tract of mammals it was easy enough to obtain a fair amount of some substance which was sure to sell well. It is said that a stone weighing four ounces was once sold in this country (or at any rate in Europe) for £200.
"There can be no doubt," observes Mr. Blanford, "thatC. aegagrusis one of the species, and probably the principal, from which tame goats are derived."
Fig. 176.
Fig.176.—Japanese Goat Antelope.Nemorrhaedus crispus.×1⁄12. (FromNature.)
The Chamois (Rupricapra) and the Goral (Nemorrhaedus) are best described as Goat-like Antelopes; but, as already said, it is difficult to split up the Bovidae satisfactorily. The Rocky Mountain Goat,Haploceros montanus, is a large Goat-like creature,which has the peculiarity of having the shortest cannon bones of any Ruminant. Its name denotes its range.
Fig. 177.
Fig.177.—Goral.Nemorrhaedus goral.×1⁄12. (FromNature.)
The Musk Ox,Ovibos moschatus, has been thought to be on the borderland between the Sheep and Oxen, as indeed expressed in its scientific name. It is a purely Arctic creature, now confined to the Nearctic region; but it formerly existed in the Arctic regions of Europe.
The anatomy of the "soft parts" of this genus has lately been investigated by Dr. Lönnberg.[210]The animal has no foot glands such as occur inOvis. Its kidneys, however, are non-lobate, and it has orbital glands. The cotyledons of the placenta are unusually large, and the cow has the "primary four" teats. It cannot, in fact, be definitely referred to either the Caprine or the Bovine section of the Cavicornia, and while possibly most allied toBudorcas, it may be regarded, at least for the present, as entitled to form a separate sub-family of its own. The muzzlehas a slight naked strip above the nostrils, as in the Sheep, but there is no fissure of the upper lip.
The origin of the Artiodactyla is placed by Cope in the familyPantolestidae,[211]allied to the genusProtogonodonof the Condylarthra. As, however, this family is represented by but a few back teeth and a fragment of the hind-foot, it seems premature to regard it as the necessary starting-point of the Bunodont and Ruminant groups.
Fam. Anthracotheriidae.—This well-known and ancient family consists of creatures of for the most part a Pig-like form, with teeth approaching the selenodont shape, and a complete dentition. The carpals, tarsals, metacarpals, and metatarsals are all free. The toes are four (or five) to each foot, with the outermost beginning to be reduced. These of course are all generalised and primitive characters, pointing nowhere in particular, except, of course, to an Artiodactyle stock, on account of the teeth and the two predominating toes.
The type genus of the family,Anthracotherium, is not, as its name might seem to denote, a relic of the Carboniferous period; its remains were found in lignite, which may also show that it was at least semi-aquatic in habit. Its form, however, must have been Pig-like, so at least one would presume from the elongated skull and shortish legs. There were species as great as a Rhinoceros, and smaller forms. The genus began in the Oligocene and continued down to the Pliocene. It is known from Europe, Asia, and America.
The skull is long with a prominent sagittal crest. The facial part is also very long, and the orbits are not closed by a bony ring. The premolars are simple teeth; the molars distinctly bunodont with a tendency in one or two to the selenodont condition. The canines are powerful, as are also the incisors. The scapula has been specially compared with that of the Camel. It has no acromion, which is usually though not always absent in Ungulates. An ally of the present animal, for instance, the Hippopotamus, has the acromion developed. The radius and ulna, the tibia and fibula, are all fully developed.
Ancodus(orHyopotamus, as it has been called) is also Oligocene in range, and its remains have been found in the same countries as have those ofAnthracotherium. Both genera are indeed closely allied.Ancodusseems to be a more slightly-built creature. The skull looks weaker, but presents much the same features of organisation. InA. velaunus, a species found in French rocks, a metacarpal of digit I. was present in the manus, whileA. brachyrhynchushad a completely five-fingered manus.
The Miocene genusMerycopotamus(from the lower layers of the Siwalik formation in India) is more distinctly selenodont than the forms already discussed. On this ground it has been placed in a separate sub-family. As, however, in other respects it does not depart from the Anthracotherian type of structure, this proceeding seems to be hardly necessary. There are two species known, of which one,M. nanus, is, as its name denotes, a dwarf form.
Fam. Caenotheriidae.—While the last family consisted of animals rather more akin to the Pigs, the present is more Pecorine in its characters. The molars are selenodont; but as in the Tragulidae the premolars are more of the nature of cutting teeth. The dentition, like that of so many of these early Ungulates, is complete, and the canines are not prominent. The feet are four-toed, the lateral toes not reaching the ground.
The principal genus is the Eocene and MioceneCaenotherium. Of this genus there were a considerable number of species all European in range, and of small size—not more than a foot or so in length. Their small size is suggestive of the Chevrotains. In the skull the orbital cavity is nearly or quite surrounded by bone, and the tympanic bulla is large and inflated. A common feature of Artiodactyles, a failure of the nasals and maxillae to meet at the side of the face, is to be seen in this ancient forerunner of the Pecora.
Plesiomeryx, also European, and from the same geological horizon, is a very closely allied form.
Fam. Xiphodontidae.—This family consists of slender, small Artiodactyles which are, like the Caenotheriidae, related to the Pecora. They are confined in their range to Europe.
The type genusXiphodonhas selenodont molars and elongated, slender, cutting premolars. The dentition was complete and the canines not highly developed. LikeCaenotherium,Xiphodonwas a hornless creature, but with only two toes, the two lateral digits being represented by the merest rudiments of metacarpals. The other metacarpals were unusually long.
Amphimeryx(also calledXiphodontotherium) is much more imperfectly known, but belongs to this family or to that of the Caenotheriidae.Dichodonis another member of the same family.
Fam. Oreodontidae.—This family, consisting of numerous genera, is limited to the North American continent. Its range in time is from the Eocene to the Lower Pliocene. The family as a whole is to be distinguished by a number of primitive characters. The dentition is complete; the feet are four- or even five-toed; the orbit is sometimes open behind. The canines of the lower jaw are not more pronounced than the incisors. The characteristics of the group will be further developed by a consideration of some of the principal genera which are included in this family.
Oreodonis a Miocene form about as large as a Peccary. The skull has a short face with a completely-closed orbital cavity. In front of the orbit is a deep pit, not a mere deficiency of ossification, such as occurs in many Artiodactyles. This is placed on the lachrymal bone, and is in fact a lachrymal fossa, such as occurs in other forms. The odontoid process of the axis vertebra is somewhat cheese-taster shaped, as in recent Artiodactyles. There are fourteen dorsal vertebrae and a very large number of caudals. The radius and the ulna are completely separated, as are the carpals. There are five digits to the fore-limbs. The fibula is complete and independent. The hind-foot is four-toed. Several species of the genus are known.
Merycochoerusis an allied Miocene genus. It is more massive in form than the last, but otherwise does not present differences of importance.
Mesoreodonis another genus of this family which presents some curious features of organisation. In the skull and teeth there is nothing very noteworthy, but the hyoid is remarkable. This appendage of the skull is by no means always preserved, and when it is, it might be denied that it belonged to any particular skull. In the present case there appears to be no doubt as to the identity of the bones, which resemble the corresponding bones of the Perissodactyla much more than they do those of other Artiodactyles. Associated with the bones an ossifiedthyroid cartilage of the larynx was found. As the skull was that of a male, this character may be a sexual one. It is quite comparable to the ossification of the same cartilage in the American monkeyCallithrix. "The function of the bone," observes Professor Scott,[212]"was probably similar to that performed by the enormously-inflated basihyal of the howling monkeys, and must have given to these animals most unusual powers of voice." Another important anatomical fact aboutMesoreodonis the apparent existence of a clavicle. It is of course conceivable that the remains of some other animal have got mixed up with that of the individuals upon which the present genus is founded; but failing that, here is a clavicle in an Ungulate. The spine of the scapula possesses a metacromion. This greater development of the spine of the scapula in Artiodactyles than in Perissodactyles is, it is suggested, to be correlated with the earlier loss of the clavicle in the latter group of Ungulates.
Cyclopidius(synonymous withBrachymeryx) is a kind of pug form ofOreodon. The skull is short and broad, and the end of the snout a little turned up. The upper incisors are small and drop out early. On each side of the nasals is a large oval vacuity which is perhaps to be compared to the lateral deficiency to be found in other Artiodactyles. One species of this singular-looking form is appropriately calledC. simus.
Other allied genera areMerychyusandLeptauchenia. The former extends as far down as the Lower Pliocene, and is thus one of the newest forms of Oreodontidae.
Agriochoerus[213](Fig. 178) is placed in a separate sub-family from the types which have just been considered. It is Miocene in range. It differs fromOreodonand its closer relatives by the fact that the orbit is open behind and not closed. The most remarkable fact about this creature is that the terminal phalanges of the digits (five in the fore- and four in the hind-feet) being pointed, seem to suggest their encasement with claws rather than hoofs. The pollex, though small, seems to have been opposable. As with other Oreodonts, the molars are selenodont. The premaxillae are toothless—at least in adults, for two teeth are present in theyoung. There are several species.Agriochoerus, likeOreodonand primitive Ungulates in general, had a long tail. The genus thus shows a mixture of ancient and specialised characters.
Fig. 178.
Fig.178.—Skeleton ofAgriochoerus latifrons. × ⅛. (After Wortman.)
The most ancient form of Oreodont isProtoreodon. This is Eocene, and became extinct during that period. It had a complete dentition, open orbit, and no lachrymal fossa. The fore-feet were five-toed, the hind four-toed.
Fam. Anoplotheriidae.—This family is entirely Eocene in point of time, and is unknown outside Europe. The dentition of the group is complete; the molars are seleno-bunodont, like those of the Anthracotheriidae. The bones of the carpus, tarsus, metacarpus and metatarsus are all free; the toes are four to two in number on each foot. The orbit is widely open behind. The tail is long, as inXiphodon, etc.
These general characters only just serve to differentiate the family; but they illustrate its archaic character, in which it resembles the Xiphodontidae, and even more the Anthracotheriidae. A survey of some of the genera which have been assigned to the family will bring out other features in the organisation of these very ancient Artiodactyles.
Anoplotheriumis so called on account of the fact that it is, like all ancient Artiodactyles, without horns or claws. Tusks it might have, but as a matter of fact has not. There are, as in Artiodactyles generally, nineteen dorso-lumbar vertebrae; the long tail has numerous chevrons. The shoulder blade has a well-marked acromion and a distinct coracoid process; it is wide proximally. The bones of the fore-arm and fore-leg are, as is usual in primitive Artiodactyles, separate.
In the skull the chief features, in addition to that mentioned in the definition of the family, are the large size of the paroccipital processes; there is no fossa lachrymalis or deficiency in the side of the face. The animal is three-toed, both in the fore- and hind-limbs. The second toe is nearly as large as the Artiodactyle third and fourth. There are tiny rudiments of the two remaining fingers. The hind-foot is also three-toed, and there is a trace of the hallux. The fingers are so widely separated and divergent from each other that it has been suggested that the animal had webbed feet and inhabited marshes, in which it swam by the aid of its long tail. The creature was the size of a Tapir.
Closely resemblingAnoplotheriumare a number of other genera.
Diplobune( =Hyracodontotherium) was much like the last, but was a more delicately-formed animal. The fingers and toes (three of each) end in such sharply-pointed phalanges that claws seem to be almost suggested. There are several species of this genus.Dacrytheriumdiffers by the presence of a lachrymal fossa.
Dichobunehas four-toed extremities, of which the lateral ones are more slender and shorter than the two middle ones. As in other Anoplotheriidae, the anterior premolars are furnished with a sharp cutting edge.
Aquatic Mammalia, with but few scattered hairs; hind-limbs absent; fore-limbs paddle-shaped; tail flattened, and eitherWhale-like or rhomboidal to circular in form. Nostrils on upper surface of not specially-elongated snout. Clavicles are absent. The scapula has the normal mammalian form, with a well-developed and roughly median spine. The bones of the arm and hand articulate together, as in land animals; the phalanges show at most traces of increase in number above the normal. Pelvis represented by a vestige, more highly developed in some fossil than in recent forms. Stomach complex, consisting of several chambers. Lungs simple and not lobulated. Diaphragm oblique and very muscular. Brain peculiar in form and but slightly convoluted. Testes abdominal. Teats two, and pectoral in position. Placenta non-deciduous and zonary.[214]
This limited group consists of purely aquatic forms, which are both marine and fresh-water in their proclivities. They have been placed in the immediate vicinity of the Whales; but it is now believed by most zoologists that the likenesses which they undoubtedly show to the Cetacea are of an adaptive kind and related to their similar mode of life. The group is a readily-definable one. Externally they are marked by their dark coloration, somewhat Whale-like though of clumsier build, and by the total absence of external ears and hind-limbs; the latter are, however, as will be pointed out shortly, marked by certain rudimentary bones. There is a flattened tail, which in the Dugong andRhytinais precisely like that of a Whale. It is interesting to note that the former genus, whose tail is, judging it at least by the standard of the Whales, more completely modified for the aquatic life, should also show other features which indicate their longer life as marine creatures. For the flippers are more Whale-like in that the fore-arm is completely enclosed within the body, or nearly so, and the nostrils have a more decidedly superior position than in the Manatee. The fore-limbs of this group, as may be inferred from what has just been said, are flipper-like; but, contrary to what we find in Whales, the phalanges do not as a rule show any traces of multiplication, so characteristic a feature of the Cetacean hand, and the individual bones are connected by well-formed joints. Beneath the thick skin, which is sparsely provided with stout hairs in the Dugong, is a layer of blubber. Dr. Murie has called attention to the fact that this layer in theManatee[215]differs from the blubber of the Whale in that there is no free oil anywhere.[216]
The skeleton of the Sirenia is strong and massive, thus contrasting with the loosely-textured bones of the Cetacea. The cervical vertebrae are, as a rule, free, but the second and third are fused inManatusand the extinctHalitherium. It is noteworthy that inRhytinathe cervical vertebrae have the exceedingly thin centra that characterises the neck vertebrae in Whales. The ribs are most of them firmly articulated by two heads. The breastbone is generally reduced, as in Whales; and but few ribs are attached thereto. The vertebrae, moreover, are well locked together by zygapophyses, and not loosely attached as in Whales.
The shoulder blade is long and narrow, and not unlike that of the Seals. It is totally unlike the peculiarly-modified scapula of the Whale tribe. But, as in the latter, there are no clavicles.
The hind-limbs are only represented by the pelvis; and this is a rudimentary structure, varying, however, in the degree of its degeneration. That of the extinctHalitheriumrecalls the pelvis of the Rorqual. There is a single triradiate bone with an acetabular cavity for the rudiment of the femur in the centre; it suggests that here the three normal elements of the pelvis have become fused into a single bone. In the Dugong there are two small bones on each side.
The Manatees (Manatus)[217]are found in the fresh-waters and along the Atlantic coasts of South America and Africa. It appears that there are four species, of which one only is African, the others American. Report asserts the former occurrence of this genus on the shores of St. Helena.
The Manatee is provided with only six cervical vertebrae, a fact which distinguishes it from the other existing genera of its group. A remarkable feature which it exhibits is the large number of molar teeth. These apparently go on increasing indefinitely during its life, the suggestion being that they are worn away by the nature of the food—algae with much sand intermixed. As many as twenty molar teeth have been counted in one half of the jaw, and there is no reason to forbid the assumption that theymay get still more numerous. This large number of grinding teeth is obviously suggestive of the Whales, with which the Sirenia are believed by some to be allied. It is at least a remarkable coincidence that these two aquatic groups of mammals should both have assumed the same indefinite tooth formula. It is correct to say assumed, since extinct forms of Manatees, such asHalitheriumandProrastoma, have not a continuous succession of molars. The brain of the Manatee is, contrary to the usual arrangement among aquatic mammals, smooth, and only marked by one or two fissures.
The Manatee[218]is black in colour, its thick skin being wrinkled. The animal is assisted in feeding by a curious mechanism of the upper lip; this is split in two, and the two halves, which are furnished with strong bristles, can play upon each other like the points of a pair of forceps. The flippers are furnished with nails, save inM. inunguis, but in the nailed forms it is not every finger which is thus armed.
Fig. 179.
Fig.179.—Skeleton of Dugong.Halicore australis.(After de Blainville.)
Halicore,[219]the Dugong, is an entirely Oriental and Australianform; there appears to be but a single species, though more than one name has been given to supposed distinct species. As already mentioned, it differs from the Manatee in the possession of a Whale-like tail; the nostrils, too, are more upon the upper surface of the head, and there are no nails upon the flipper. The peculiar cleft lip of the Manatee is not so well developed in the Dugong, but there are traces of it; and in the foetus the likeness to the Manatee in this respect is very striking. It would thus appear thatHalicoreis a stage in advance uponManatus; that the remarkable mechanism of the lip of the latter has been possessed, but has been lost, by the Dugong. The skull of the Dugong is distinguished by the stout premaxillary bones, which bear a tusk in the male. In the female the tooth is there, but is lodged within the bone. This incisor has a milk forerunner. The back teeth of the Dugong (there are no canines) are few in number (four or five, even six), thus showing a gradual reduction when compared withManatus; and this culminates in the toothlessRhytina. It is also interesting to notice that in the massive lower jaw there are traces of an incisor. Were this to be developed into a tusk, the jaw would present a curious resemblance to that ofDinotherium.
The Dugong,H. dugong, has the reputation of being the original of the mermaid legends, since the young is held to the pectorally-situated breast with one flipper. "But it should be remembered," justly observes Dr. Blanford, "that stories of beings half man or woman, half fish, are as common in temperate as in tropical seas, and that some of them are more ancient than any European knowledge of the Dugong."
Extinct Sirenians.—The earliest genus that can be with certainty referred to this order is the OligoceneProrastoma. This genus, though offering no particular skull-characters that assist in the determination of the much-debated affinities of the Sirenia, shows a remarkable condition of the teeth that may afford a clue. The speciesP. veronense, recently described by Mr. Lydekker,[220]is founded upon a fragment of the skull which contains two teeth apparently representing the third and fourth upper milk molars. The interest attaching to these teeth lies in the fact that they clearly exhibit the buno-selenodont condition characteristic of certain early Artiodactyles, e.g.Merycopotamus.
Halitheriumis a later genus, which is known by the nearlycomplete skeleton. The skull is like that of other Sirenia, with the down-turned premaxillary region. But the nasal bones, lost, or at least rudimentary, in recent forms, are well developed; the likeness of ancient to living forms in this respect being exactly paralleled by the Zeuglodonts, when compared with recent Whales. The vertebral centra exhibit distinct epiphyses, which have disappeared in living Sirenians. The cervical vertebrae are seven, of which the second and third are occasionally fused. There are nineteen pairs of ribs, and there are three lumbar vertebrae. The sternum consists of three separate pieces. There is a rudimentary femur.
The recently-extinct Steller's Sea-cow, belonging to the genusRhytina, was a huge beast, seen in the flesh up to nearly the end of the last century. It frequented the shores of Bering's Straits. Its remains occur in the peat on the shores of those seas. It reaches a length of some 20 to 30 feet. The external characters were much like those of other recent Sirenians. The nostrils were above the fore part of the snout, the latter being truncated and obtuse. The tail was of the Cetacean pattern, and thus like that ofHalicore. The head of this Sirenian was small, and the teeth had entirely vanished save for the apparent existence as transitory structures of two small incisors in the upper jaw. The absence of teeth was compensated by the presence of a horny palate for the trituration of the sea-weeds which constituted the food of Steller's Sea-cow. The fore-limbs seem to have possessed no nails, but were covered at the extremity with short, bristly hairs, no doubt serving the purpose of keeping the animal moored in safety to the slippery beds of Fucus upon which it browsed.
There are nineteen pairs of ribs. The vertebrae of the cervical region are the customary seven, and the centra are thin and plate-like as in the Cetacea, the animal being thus short-necked like those marine creatures.
Aquatic Mammalia of fish-like form; tail expanded into horizontal flukes; a fatty dorsal "fin" present in most species; anterior limbs converted into fin-like paddles; posterior limbs only represented by skeletal rudiments. Hairy covering reduced to a few isolated hairs in the neighbourhood of the muzzle. Nostrils represented by the single or double blow-hole, nearly always situated far back upon the skull. Bones of loose texture and much impregnated with oil. The skull has a greatly-developed facial portion; supra-occipital bones meeting the frontal by overgrowing, or growing in between the parietals; bones surrounding the organ of hearing loosely attached to the skull, the tympanics of peculiar cowrie-shell form. Coronoid process of mandible absent, or very feebly developed. Teeth, when present, few or numerous, always of simple conical form, with at most traces of additional cusps (Inia); if absent their place taken by whalebone. Cervical vertebrae of short antero-posterior diameter, often more or less completely welded together into a single mass. Articulations between dorsal and other vertebrae feeble. Scapula peculiarly flattened; acromion strongly developed as a rule, but arising from a slightly-marked spine; coracoid process generally strongly developed. Phalanges of digits always more numerous than in other mammals. Clavicles absent. Stomach complex, consisting of at least four and often more chambers. Lungs simple and non-lobulated. Diaphragm obliquely set and verymuscular. Brain much expanded transversely and well convoluted. Testes abdominal. Teats two, inguinal in position. Placenta diffuse and non-deciduate.
The Whales and Dolphins, which constitute this order, form an assemblage which is easily characterised by reason of the fact that their affinities to other groups of Mammalia are so doubtful that they furnish matter rather for speculation than for authoritative statement. Some hold that they resemble in certain points the Ungulata; while others again see in them the culminating term of a series which commences with such a form as the Otter, and of which the Seals and Sea-lions are intermediate stages. A third opinion is that the Whales have arisen from some low mammalian stock, too primitive to be assigned to any existing order of mammals. Palaeontology, as will be seen later, throws no light whatever upon their origin. This matter has already been referred to (see p.120) in considering the position of the Cetacea.
The Whales include the most gigantic of all the orders of vertebrated animals. No creature living or extinct is so large as the Sibbald's Rorqual, which attains to a length of some 85 feet, or perhaps even rather more. On the other hand we have what are by comparison minute forms. Apart from the possibly problematicalDelphinus minutus, stated to be only 2 feet in length, we have as a minimum 3 or 4 feet. The size of the Cetacea has been subjected to much exaggeration. The first duty of a Whale, observed the late Sir William Flower, is to be large; and Natural Historians, in the recent as well as in the remote past, have not hesitated to put very round numbers upon the dimensions of the larger members of the order. We may perhaps pass over Pliny's "fish called balaena or whirlpool, which is so long and broad as to take up more in length and breadth than two acres of ground," and a number of analogous exaggerations, which gradually dwindled down to the dimensions just stated of the great Rorqual. M. Pouchet has made the ingenious suggestion that the statements of the ancients may have been nearer the truth than observations of to-day would have us believe; he pointed out justly that in former times Whales were not so relentlessly pursued as during the last century; the inference being that they may have lived to a greater age, and attained a more colossal bulk. The more modern exaggerations in thedimensions of the bigger Whales are probably due to the fact that measurements have been taken, not in a straight line from snout to tail, but along the bulging sides of the Cetacean, rendered even more convex than in nature by decomposition, and by pressure due to the immense tonnage of the creature.
The Cetacea are the most perfectly aquatic of all mammals; they never leave the waters which they inhabit. It is true that legends have represented them as pasturing upon the shore—Aelian spoke of Dolphins basking in the sun's rays upon the sand; and the "Devil Fish" of California,Rhachianectes(see p.357) has given rise to improbable stories—but they are apparently only legends. Indeed a stranded Whale cannot live long, for it is unable to breathe, the comparatively feeble breast being crushed by its own weight. In accordance with the purely aquatic habit, we find a modification of the outward form of the body (and as we shall see later of many of the internal organs), which renders the Cetacea externally unlike all other mammals. The form is fish-like, the fore-limbs are paddles, the tail is expanded into two horizontal flukes, which serve to propel the creature through the water.