This order is mainly Australian at the present day, using the term of course in the "regional" sense (see p. 84); the only exception indeed to this statement is the occurrence of the genus _Caenolestes_ in South America. But it is now known that Diprotodont Marsupials formerly existed in the same part of the world.

[Ill.u.s.tration]

FIG. 64.--Bones of right foot of Kangaroo (_Macropus bennetti_). _a_, Astragalus; _c_, calcaneum; _cb_, cuboid; _e_^3, ento-cuneiform; _n_, navicular; _II-V_, second to fifth toes. (From Flower's _Osteology_.)

{130}

[Ill.u.s.tration]

FIG. 65.--Skeleton of Wallaby (_Macropus ualabatus_). The scapula is raised somewhat higher than in nature. The end of the tail is omitted. The head of the femur has been separated from the acetabulum. _acet_, Acetabulum; _acr_, acromion process; _ast_, astragalus; _cal_, calcaneum; _cbd_, cuboid; _chev_, chevron-bones; _cl_, clavicle; _cun_, cuneiform of carpus; _epi_, epipubis; _fb_, fibula; _fem_, femur; _hd_, head of femur; _hu_, humerus; _il_, ilium; _isch_, ischium; _obt_, obturator-foramen; _orb_, orbit; _pis_, pisiform; _pub_, pubis; _rad_, radius; _rb_^1, first rib; _rb_^{13}, last rib; _sc_, scapula; _st_, sternum; _tb_, tibia; _troch_, great trochanter of femur; _uln_, ulna; _unc_, unciform; _IV_, fourth toe.

(From Parker and Haswell's _Zoology_.)

FAM. 1. MACROPODIDAE.--This family contains the Kangaroos, Wallabies, Rat-Kangaroos, and Tree-Kangaroos. With the exception of _Dendrolagus_ the family is terrestrial, and its numerous species progress by leaps effected by the long hind-limbs, which are decidedly, often greatly, longer than the fore-limbs. In the hind-limb the fourth toe is very long and strong; the fifth moderately so; the second and third are slender and united by skin.

The tail is always long, but differs in its characters from {131} genus to genus. The stomach is much sacculated. The dental formula is I 3/1 C (1 or 0)/0 P 2/2 M 4/4. The atlas is often open below, forming thus an incomplete ring.

Though the number of the incisor teeth in the adult Diprotodonts is never more than three on each side in each jaw, more numerous rudiments are present. Mr. M. Woodward[76] has lately investigated the subject with interesting results. He finds that many species present decided traces of two additional incisors, raising the total to that which characterises the Polyprotodontia; but in two cases, viz. _Macropus giganteus_ and _Petrogale penicillata_, a sixth is present, the total number being thus in excess of that found in any other Marsupial. This, as the author himself admits, proves too much. No mammal is known which in the adult condition has so many incisors; nor do the fossil Mammalia help us to get over the difficulty; even among reptiles it is not usual for so many teeth to occur upon the premaxillaries.

It is a curious fact that the two long lower incisors can be used after the fashion of a pair of scissors, or rather a pair of shears. Their inner edges are sharpened, and they are capable of some motion towards and away from each other; by their means gra.s.s is cropped.

The stomach of _Macropus_ (and of other allied genera) is peculiar by reason of its long and sacculated character; the oesophagus enters it very near the cardiac end, which is bifid. Messrs. Schafer and Williams[77] have shown that the squamous, non-glandular epithelium of the oesophagus extends over the greater part of the stomach, only the pyloric extremity and one of the two cardiac caeca being lined with columnar epithelium.

The Macropodidae are clearly divisible into three sub-families, which are distinguished by marked anatomical characters.

In the sub-family MACROPODINAE (including the genera _Macropus_, _Petrogale_, _Lagorchestes_, _Dorcopsis_, _Dendrolagus_, _Onychogale_, and _Lagostrophus_) there is no hallux, and the tail is hairy. The oesophagus enters the stomach near the cardiac end. The caec.u.m when short has no longitudinal bands; the liver has a Spigelian lobe.

The second sub-family, POTOROINAE or HYPSIPRYMNINAE (including the genera _Potorous_, _Aepyprymnus_, _Bettongia_, and {132} _Caloprymnus_), consists of smaller animals than the Macropodinae, which, however, resemble them in having no hallux, but a hairy tail. The oesophagus enters the stomach near the pyloric end of that organ. The caec.u.m, though short, has lateral longitudinal bands. The liver has no special Spigelian lobe. The canines are always present, being rarely so in Macropodinae, and are usually well developed.

The third sub-family, that of the HYPSIPRYMNODONTIDAE, is doubtfully referable to the family; it consists of but one genus _Hypsiprymnodon_, which is in many points more like a Phalanger than a Kangaroo. It has an opposable hallux and a non-hairy, but scaly, tail. It has canines in the upper jaw.

[Ill.u.s.tration]

FIG. 66.--Red Kangaroo. _Macropus rufus._ 1/18.

SUB-FAM. 1. MACROPODINAE.--The genus _Macropus_ includes not only the Kangaroos but also the Wallabies, which are really indistinguishable, though they have sometimes been placed in a separate genus _Halmaturus_.

The genus thus enlarged contains twenty-three species. It may be thus characterised: the ears are long, the rhinarium is usually naked, but in _M. giganteus_ and others a band of hairs descends to the upper lip; a naked band extends from the ankle to the pads on the digits, which is interrupted in _M. rufus_ by a band of hairs just in front of the digits.

The mammae are four. The tail is not bushy, {133} but is crested in _M.

irma_. They are for the most part found on the Australian continent, but some species are found in the islands to the north which belong to the Australian region. Thus _M. brunii_, which is of interest as the first Kangaroo seen by a European, is a native of the Aru islands. A specimen of this animal, which was then living in the garden of the Dutch governor of Batavia, was described by Bruyn in the year 1711. _M. rufus_, the largest member of the group, is remarkable for the red secretion which adorns the neck of the male. It is caused by particles which have the appearance and colour of carmine. _M. giganteus_ is not, as its specific name might imply, the "giant" of the race; its dimensions are given as 5 feet, while _M.

rufus_ is said to attain a length of 5 feet 5 inches, exclusive (in both cases) of the tail.

The account which Sir Joseph Banks gives[78] in his diary of the Kangaroo is interesting, since he was one of the first naturalists to see that creature. In July 1770 it was reported to him that an "animal as large as a greyhound, of a mouse colour, and very swift" had been seen by his people.

A little later he was surprised to observe that the animal "went only upon two legs, making vast bounds just as the jerboa does." The second lieutenant killed one of these Kangaroos, of which Sir Joseph Banks wrote that "to compare it to any European animal would be impossible, as it has not the least resemblance to any one I have seen. Its fore-limbs are extremely short and of no use to it in walking; its hind, again, as disproportionately long; with these it hops seven or eight feet at a time, in the same manner as the jerboa, to which animal indeed it bears much resemblance, except in size, this being in weight 38 lbs., and the jerboa no larger than a common rat." The beast was killed and eaten, and proved excellent meat. Sir Joseph Banks' observations upon the leaping of the Kangaroo are of interest, because it is often a.s.serted that the tail is largely made use of as a third foot or as a support. Mr. Aflalo declares in the most positive way that after repeatedly examining the tracks upon soft sand immediately after the animal had pa.s.sed, not the very faintest trace of the impression of the tail could be discovered. The leaps of a big Kangaroo seem to be somewhat greater than is recorded {134} by Banks. It is said that 15 or even 20 feet are covered at a bound, and in bound after bound. But in walking slowly it can be readily seen from an inspection of Kangaroos at the Zoological Society's Gardens that the animal does rest upon its tail, which with the hind-legs forms a tripod.

_Petrogale_ with six species comes next to _Macropus_, and is indeed only to be differentiated from it by the thickly-haired and more slender tail, which is not used, as it is sometimes in the Kangaroos, as an extra hind-limb. The Rock-Kangaroos live among rocks, which they climb, and from which they leap; and the tail acts rather as a balancing pole. The most elaborate account of the anatomy of _Petrogale_ known to me is by Mr.

Parsons.[79] The dent.i.tion as given by Mr. Thomas is I 3/1 C 0/0 Pm 2/2 M 4/4--that of _Macropus_ without the occasionally occurring canine of the upper jaw. The osteological characters which separate it from _Macropus_ are quite insignificant. Mr. Parsons mentions a wormian bone, "os epileptic.u.m," at the junction of the coronal and sagittal sutures. It was found to occur in two out of five skulls examined, and appears not to occur in other Kangaroos. The palatine foramina of _Petrogale_ are so large that the posterior part of the bone is only a narrow thickened ridge. The small intestine of _P. xanthopus_ is 102 inches long, the large intestine 44 inches. The caec.u.m has a length of 6 inches, and is not sacculated, differing in this from the caec.u.m of _Macropus major_. The best known species are _P. xanthopus_ and _P. penicillata_. The genus is confined to Australia itself, and does not enter Tasmania.

_Onychogale_ includes the so-called "Nail-tailed Wallabies," which have a thorn at the end of the tail, reminding one of the Lion and the Leopard, whose tails have a similar armature. The m.u.f.fle is hairy. Three species are allowed by Mr. Thomas.

_Lagorchestes_ has, like the last genus, the rhinarium, _i.e._ that part of the nose immediately surrounding the nostrils, hairy instead of smooth as in the Kangaroos proper. It is distinguished from _Onychogale_ by the absence of the terminal callosity to the tail, which is rather short. The name Hare-Kangaroo is given to the members of this genus (three species) on account of their exceeding fleetness. This genus is limited to Australia itself. _L. conspicillatus_ is said to present "a remarkable {135} resemblance to the English hare," and _L. leporoides_ was so called by Gould on account of general appearance as well as face.

_Dorcopsis_ has shorter hind-legs than _Macropus_, and a naked m.u.f.fle. The ears are small. The structure of _D. luctuosa_ has been studied by Garrod,[80] who pointed out the existence of four enlarged hair follicles on the neck near the mandibular symphysis. These are, however, represented in the next genus _Dendrolagus_, and occur also in _Petrogale_. The limbs are not so disproportionate as in _Macropus_, and the tail is naked at the tip.

_Dorcopsis_ and the next genus to be described, _Dendrolagus_, differ from _Macropus_ and its immediate allies, _Petrogale_ and _Lagorchestes_, in a number of anatomical points. In the first place, the premolars are twice the size of those of _Macropus_, and they have a characteristic pattern not observable in the Kangaroos. This consists of a median ridge (the whole tooth being rather prismatic in shape), with lateral ridges at right angles to it. The upper canines are developed, but are minute.

The stomach is not quite like that of _Macropus_, though built upon a similar plan. The blind cardiac extremity is a single, not a double cul-de-sac; in this it is like that of _Petrogale_. The distribution of the squamous, white, oesophageal epithelium is very much like that of _Dendrolagus_. In both genera the orifice of the oesophagus into the stomach is guarded by two strong longitudinal folds, which run for some distance towards the pylorus. In _Dendrolagus_, at any rate, this tract is bordered on each side by glandular patches. In _Dendrolagus_, moreover, the squamous epithelium does not extend into the cardiac cul-de-sac. This latter is separated from the rest of the stomach by two slightly diverging folds, which are faintly represented in _Petrogale_ and in _Halmaturus_. In the last two genera the folds surrounding the oesophageal orifice are but slightly represented; better in _Halmaturus_ than in _Petrogale_. But there are not the patches of glands already referred to. The small intestine of _Dorcopsis_ is 97 inches in length, the large being 32, _i.e._ proportionately long, as in Marsupials generally. The small caec.u.m (2 inches) is not sacculated.

The spleen is Macropodine, being [81]-shaped or [82]-shaped. The differences between _Dorcopsis_ and the evidently closely allied _Dendrolagus_ will be further considered under the description of {136} the latter. _Dorcopsis_ is confined to New Guinea, and contains three species, viz. _D. muelleri_, _D. luctuosa_, and _D. macleani_. _D. muelleri_ has a striking resemblance to _Macropus brunii_, with which it has been confounded. Though intermediate between _Macropus_ and _Dendrolagus_, these Kangaroos are not arboreal.

The genus _Dendrolagus_ is remarkable for its un-kangaroo-like habit of living in trees. In accordance with this change of habit is a relative shortening of the hind-limbs, a feature which begins to be observable in _Dorcopsis_. "The general build," writes Mr. Thomas, "is of the ordinary mammalian proportions, not macropodiform at all." The m.u.f.fle is not naked for the greater part, though the shortness of the hairs gives that effect.

As in _Dorcopsis_, but not as in _Macropus_, the bulla tympani is not swollen. There are altogether five species, the fifth, _D. bennetti_, having been lately described from specimens living in the Zoological Society's Gardens.

[Ill.u.s.tration]

FIG. 67.--Tree-Kangaroo. _Dendrolagus bennetti._ 1/12.

The anatomy of this genus has been described by Owen for _D. inustus_,[83]

and by myself for _D. bennetti_. The stomach, which {137} has a single, not bifid, cul-de-sac, is sacculated by two princ.i.p.al bands and other subsidiary ones. Its internal structure has already been to some extent described. The spleen of _D. bennetti_ is remarkable for the fact that it is not [84]-shaped, whereas _D. inustus_ agrees with other Macropodines in the form of this organ. The small intestine of _D. bennetti_ is 95 inches long, the large 38. The caec.u.m appears to differ in the two species; it is smaller in _D. bennetti_, where it is only 2 inches in length. The most remarkable feature of the liver is the large size of the left lateral lobe and the bilobed condition of the Spigelian lobe; this at least was the case with _D. bennetti_. A recently-described species[85] has been attentively studied in its native haunts by Dr. Lumholtz.[86] It lives in the highest parts of the mountainous scrubs of Queensland, where it moves quickly on the ground as well as among the trees. It is hunted with Dingos by the "blacks," and is eaten by them.[87]

_Lagostrophus_ is a generic name that has been proposed by Mr. Thomas for a small Wallaby 18 inches in length, which is distinguished by the fact that the long claws of the hind-limbs are entirely hidden by long and bristly hairs; the m.u.f.fle is naked; there is no canine. The bullae are swollen.

There is but one species of the genus, _L. fasciatus_, a native of West Australia.

SUB-FAM. 2. POTOROINAE.--_Aepyprymnus_ and the other genera placed in this sub-family are known by the vernacular name of Rat-Kangaroos, or sometimes Kangaroo-Rats. The latter term has been called "incorrect," though it is just as good as the former, both of them in fact being inaccurate as implying some likeness to or relation with a Rat. The present genus has a partially hairy rhinarium; the auditory bullae are not swollen. It contains but one species, _Ae. rufescens_, a native of Eastern Australia, which is distinguished by its very long hind-feet.

_Bettongia_ has long hind-feet as in _Aepyprymnus_, but the rhinarium is entirely naked instead of being partially hairy, while the ears are much shorter. The genus, which contains four species, is remarkable as being the only ground-living mammal with a prehensile tail, which it uses to carry gra.s.s, etc. {138} _B. lesueuri_ burrows in the ground, often to so great a depth as 10 feet. The genus occurs in Tasmania as well as in Australia.

_Caloprymnus_, with one species, is a genus inst.i.tuted by Mr. Thomas in his Catalogue of Marsupials for a form (_C. campestris_) which combines in a remarkable way the characters of _Aepyprymnus_, _Bettongia_, and _Potorous_. The external characters and the general shape of the skull are as in _Bettongia_, while the molars have the structure of those of _Aepyprymnus_. The last premolar is as in _Potorous_.

Of the genus _Potorous_ there are three species, which are Tasmanian as well as Australian. Unlike the other Rat-Kangaroos, the hind-feet are comparatively short, and the animal is therefore less addicted to jumping than its relatives. The rhinarium is naked, and the ears are of fair length.

SUB-FAM. 3. HYPSIPRYMNODONTINAE.--The Musk-Kangaroo, _Hypsiprymnodon_, is the last genus of the present family, and the only genus of this sub-family. It is intermediate between the Macropodidae and the Phalangeridae, the annectant character being mainly the hind-feet, which though they have the same long fourth digit as the Kangaroos, have it more feebly developed, and possess also an opposable hallux, which is one of the salient features in the structure of the Phalangeridae. The tail is naked and scaly; the rhinarium is entirely naked. The ears are large and not furry. The single species, _H. moschatus_, appears to feed upon insects as well as vegetables.

"Its habits are chiefly diurnal, and its actions when not disturbed by no means ungraceful. It progresses in much the same manner as the Kangaroo-Rats (_Potorous_), to which it is closely allied, but procures its food by turning over the debris in the scrubs in search of insects, worms, and tuberous roots, frequently eating the palm berries, which it holds in its fore-paws after the manner of the Phalangers, sitting up on its haunches, or sometimes digging like the bandicoots." This is Mr. Ramsay's description of the animal, which he was the first to discover.[88]

FAM. 2. PHALANGERIDAE.--The genus _Hypsiprymnodon_ bridges over the not very wide gap which separates the Kangaroos from the Phalangers. The Phalangers are Marsupials with five fingers and toes; the second and third toes are bound together by a {139} common integument as in the Macropodidae. The hallux is opposable and nailless. The tail is nearly always long and prehensile. The pouch is well developed; the stomach not sacculated; a caec.u.m is present (except in _Tarsipes_). These are really the princ.i.p.al distinctions between the two families. In addition, it may be mentioned that the lower incisors have not a scissor-like action as in the Kangaroos.

The Phalangers may be divided into four sub-families.

The first of these, that of the PHALANGERINAE, contains the genera _Phalanger_ (including _Cuscus_), _Acrobates_, _Distaechurus_, _Dromicia_, _Gymn.o.belideus_, _Petaurus_, _Petauroides_, _Dactylopsila_, _Pseudochirus_, and _Trichosurus_.

These genera agree in the following generalities:--Tail well developed, often very long; three incisors above, and at least two premolars both above and below; caec.u.m long and simple; stomach without a cardiac gland; liver not very complicated by secondary furrows, with a distinct caudate lobe; the v.a.g.i.n.al median culs-de-sac often coalesced; lungs with an azygos lobe.

[Ill.u.s.tration]

FIG. 68.--Bones of leg and foot of Phalanger. _ast_, Astragalus; _calc_, calcaneum; _cub_, cuboid; _ect.cun_, ecto-cuneiform; _ent.cun_, ento-cuneiform; _fb_, fibula; _mes.cun_, meso-cuneiform; _nav_, navicular; _tib_, tibia; _I-V_, first to fifth toes. (After Owen.)

The second sub-family, PHASCOLARCTINAE (with the Koala only), is thus characterised:--Tail rudimentary; cheek-pouches present; superior incisors three, but only one premolar above and below; {140} caec.u.m extraordinarily long; stomach with a cardiac gland; liver complicated by additional furrows, without a free caudate lobe; no azygos lobe to lungs; v.a.g.i.n.al culs-de-sac free.

The third sub-family, PHASCOLOMYINAE, contrasts with the others as follows:--Tail rudimentary; cheek-pouches present, but rudimentary; one incisor on each side above, but no additional premolars; all the teeth rootless; caec.u.m not peculiar in shape; stomach with a cardiac gland; liver complicated by secondary furrows, without a free caudate lobe; lung with an azygos lobe; v.a.g.i.n.al culs-de-sac free.

The last sub-family, TARSIPEDINAE, is thus defined:--Tail long; tongue extensile; only one premolar; molars reduced; caec.u.m absent.