The Indian species is said to live in pairs, and to give birth to one or two young at a time in the spring. Their burrow reaches a depth of some twelve feet, and terminates in a large chamber, which may be as much as six feet in diameter. A faint hiss appears to be the only sound emitted by these animals.

Remains of a large species of Manis, which are indistinguishable from the corresponding bones of the existing West African M. gigantea, are found fossil in cave-deposits in the Karnul district of Madras. This is one among several instances of the close connection between the Pleistocene and Pliocene mammalian fauna of India with the existing African fauna.

Palæomanis.-The lower Pliocene deposits of the Isle of Samos, in the Turkish Archipelago, have yielded remains of a Pangolin fully three times the dimensions of M. gigantea, upon the evidence of which the genus Palæomanis has been established.

Family ORYCTEROPODIDÆ

Teeth

External surface scantily covered with bristle-like hairs. numerous, apparently heterodont, diphyodont, and of peculiar and complex structure, being traversed by a number of parallel vertical pulp-canals. Lumbar vertebræ with no accessory zygapophyses. Femur with a third trochanter. Fore feet without pollex, but all the other digits well developed, with strong moderate-sized nails, suited to digging, the plantar surfaces of which rest on the ground in walking. Hind feet with five subequal toes. Mouth elongated and tubular. Tongue subvermiform. Uterus bicornuate. Placenta broadly zonular. Feeding on animal substances. Terrestrial and fossorial in habits. Now mainly limited to the Ethiopian region.

Orycteropus.2 The total number of permanent teeth appears to be from eight to ten in each side of the upper, and eight in the lower jaw; but they are never all in place at one time, as the small anterior teeth are shed before the series is completed behind. In the adult they number usually five on each side above and below, of which the first two are simple and compressed, the next two larger and longitudinally grooved at the sides, the most posterior simple and cylindrical. The last three in either jaw having no milk-predecessors, may be regarded as true molars. The structure of all these teeth is quite peculiar among mammals, though resembling that of some fishes. Their summits are rounded before they are worn; their bases do not taper to a root, but are evenly truncated and continually growing. Each tooth is made up of an aggregation of parallel dental systems, having a slender pulp-cavity 1 Forsyth-Major, Comptes Rendus, vol. cvii. p. 1180 (1888).

2

Geoffroy, Décade Philosophique, 1795 (teste Agassiz).

in the centre, from which the dentinal tubes radiate outwards, and being closely packed together each system assumes a polygonal outline as seen in transverse section. The small anterior teeth have milk-predecessors which are fully noticed below. Skull moderately elongated. The facial portion subcylindrical and slightly tapering. The zygoma complete and slender. The palate ends posteriorly in the thickened transverse border of the palatines, and is not continued back by the pterygoids. The tympanic is annular, and not ankylosed to the surrounding bones. The mandible is slender anteriorly, but rises high posteriorly, with a slender recurved coronoid, and an ascending pointed process on the hinder edge below the condyle, which is small, oval, and looks as much forwards as upwards. Vertebræ: C7, D13, L8, S6, C 27. The large number of lumbar vertebræ is peculiar among Edentates. Tongue less vermiform than in Myrmecophaga, being thick and fleshy at the base, and gradually tapering to the apex. The salivary apparatus is developed much in the same manner as in that genus, but the duct of the submaxillary gland has no reservoir. The stomach consists of a large subglobular cardiac portion, with a very thick, soft, and corrugated lining membrane, and a smaller muscular, pyloric part, with a comparatively thin and smooth lining. There is a very distinct ileo-cæcal valve, and a considerable-sized cæcum; also a gall-bladder. Head elongated, with a tubular snout, terminal nostrils, and small mouth-opening. Ears large, pointed, erect. Tail nearly as long as the body, cylindrical, very thick at the base, tapering to the extremity.

The reproductive organs and placentation of Orycteropus are formed upon a principle unknown in the more typical Edentates, or, in combination, in any other mammals. Thus the testes, in the one described example, were inguinal, but appeared to descend, at all events temporarily, into a scrotum; but the penis is scarcely larger than that of the Great Anteater. The uterus is still more fully bicornuate than in Manis, with its two lateral chambers opening separately into the vagina, as in certain Rodents. The placenta is broadly zonary, but it is not known whether it is deciduate or not. It might readily be derived from the diffused placenta of Manis by the abortion of the fœtal villi at the two poles of the ovum.

The Orycteropodido have long been regarded as widely different from other Edentates, their presumed affinity with the Manidæ being more or less problematical; but the discovery recently made by Mr. O. Thomas 1 that they have a milk-dentition still further emphasises their aberrant nature. According to this observer, it appears that there are normally no less than seven milk-teeth in the upper jaw, the hindmost of which is far larger than the others, 1 Proceedings of the Royal Society, vol. xlvii. p. 246 (1890).

having a rudimentary crown, and a distinct anterior and posterior root. The other milk-teeth are styliform, the four anterior ones being very minute, and separated from one another by equal intervals; the foremost of all is situated immediately behind the premaxillo-maxillary suture. In the mandible only four milk-teeth have hitherto been detected, of which the hindmost has the comparatively complex form found in the corresponding upper tooth. None of these milk-teeth appear, however, to cut the gum, so that the whole set is entirely functionless. Under the microscope these milk-teeth show signs of possessing a commencement of the remarkable histological structure found in the permanent teeth.

Mr. Thomas remarks that since "the three large posterior teeth of Orycteropus, already distinguished by their more molariform shape, do not have milk-predecessors, while all the small teeth anterior to them do, and in addition the last milk-tooth is markedly different from those in front of it, we ought apparently no longer to look upon this animal as an homodont, but instead to consider it as an originally heterodont form in which the incisors and canines have been suppressed to allow free play to the mobile vermiform tongue.

"But important as a knowledge of the presence of a milkdentition in Orycteropus is, it does not at present render any easier the difficult questions as to the phylogeny and systematic position of that animal. Although called an Edentate, it has always been recognised as possessing many characters exceedingly different from those of the typical American members of the order. It has in fact been placed with them rather on account of the inconvenience of forming a special order for its reception than because of its real relationship to them. Now, as they are either altogether toothless, or else homodont and monophyodont (apart from the remarkable exception of Tatusia), it seems more than ever incorrect to unite with them the solitary member of the Tubulidentata, toothed, heterodont, and diphyodont, and differing from them in addition by its placentation, the anatomy of its reproductive organs, the minute structure of its teeth, and the general characters of its skeleton.

"But if Orycteropus is not genetically a near relation of the Edentates, we are wholly in the dark as to what other mammals it is allied to, and I think it would be premature to hazard a guess on the subject. Whether even it has any special connection with Manis is a point about which there is the greatest doubt, and unfortunately we are as yet absolutely without any palæontological knowledge of the extinct allies of either. Macrotherium even, usually supposed from the structure of its phalangeal bones, to be related to Manis, has lately proved to have the teeth and vertebræ of a perissodactyle Ungulate, and one could not dare to suggest that ancestors of Manis, or Orycteropus were to be sought in that direction. Lastly, as the numerous fossil American Edentates do

not show the slightest tendency to an approximation towards the Old World forms, we are furnished with an additional reason for insisting on the radical distinctness of the latter, whose phylogeny must therefore for the present remain one of the many unsolved zoological problems."

The Aard-Varks (Earth-Pigs) as these creatures are commonly termed, from the name bestowed on them by the Dutch Boers of the Cape, are of nocturnal habits, sleeping during the day in their burrows, which are usually found in the neighbourhood of the tall hills or mounds made by termites. Indeed, wherever these hills are abundant it is stated there is a good chance of finding an Aard-Vark, the food of these animals consisting almost exclusively of termites and ants.

Two existing species are recognised, namely the Cape Aard-Vark (0. afra) from South Africa, and another (0. aethiopicus) from the north-eastern parts of Africa, ranging into Egypt. An extinct species has been described from the Lower Pliocene of the Isle of Samos, in the Turkish Archipelago, differing from the existing forms by the larger proportionate size of the lateral metatarsals.

Bibliography of Edentata.—No general work on the order has been published since that of Rapp (Anat. Untersuchungen über die Edentaten, 2d ed. 1852). Among numerous memoirs on special groups the following may be cited:Myrmecophagida:-R. Owen, "Anatomy of Great Anteater," Trans. Zool. Soc. vol. iv.; G. Pouchet, Mém. sur le Grand Fourmilier, 1874; W. A. Forbes, "Anat. of Great Anteater," Proc. Zool. Soc. 1882, p. 287. Megatheriida :—R. Owen, Extinct Gigantic Sloth (Mylodon Robustus), 1842; Id., "On the Megatherium," Phil. Trans. 1851-56; J. Leidy, "Extinct Sloth-tribe of North America," Smithsonian Contrib. to Knowledge, vii. 1855; H. Burmeister, Description de la République Argentine, t. iii. Mammifères, 1879,-which contains full references to various memoirs by Owen, Gervais, Reinhardt, and others. Glyptodontida :-Owen, Catalogue of Fossil Mammals, Mus. Roy. Coll. Surgeons, 1845; T. H. Huxley, "Osteol. of Glyptodon," Phil. Trans. 1865; H. Burmeister, Annales del Museo Publico de Buenos Aires, and. Descript. de la République Argentine, 1879; H. Gervais and F. Ameghino, Les Mammifères Fossiles de Amérique Méridionale, Paris, 1880,-which also contains a list of all the S. American Edentates described at that date. Dasypodido:-J. Murie, “Anatomy of Tolypeutes," Trans. Linn. Soc. vol. xxx. 1874; A. H. Garrod, Proc. Zool. Soc. 1878. For Placentation of Edentates see W. Turner, Trans. Roy. Soc. Edin. xxvii. (1873) p. 72, and Journ. Anat. and Physiol. vols. viii. and x.; A. Milne-Edwards, Ann. Sciences Nat. [6] viii. p. 1; and for brain, P. Gervais, "Formes cérébrales des Edentés," Nouv. Arch. du Muséum, tom. v. ; W. Turner, Jour. Anatomy, i. 313 (1867). For the dentition of Orycteropus see O. Thomas, "A Milk Dentition in Orycteropus," Proc. Roy. Soc. vol. xlvii. p. 246 (1890). Fuller observations on the mutual relations of the various families are given by W. H. Flower, "On the Mutual Affinities of the Animals composing the Order Edentata," Proc. Zool. Soc. 1882, p. 358.

CHAPTER VIII

THE ORDERS SIRENIA AND CETACEA

Order SIRENIA.

THE purely aquatic habits and fish-like form of the animals of this order caused them to be formerly confounded with the Cetacea, but a more intimate knowledge of their structure has shown that they really belong to a widely different type of the mammalian

class.

The head is rounded and not disproportionate in size as compared with the trunk, from which it is scarcely separated by any externally visible constriction or neck. Nostrils valvular, separate, and placed above the fore part of the obtuse truncated muzzle. Eyes very small, with imperfectly formed eyelids, capable, however, of contraction, and with a well-developed nictitating membrane. Ear without any pinna. Mouth of small or moderate size, with tumid lips beset with stiff bristles. General form of the body depressed, fusiform. No dorsal fin. Tail flattened and horizontally expanded. Fore limbs paddle-shaped, the digits being enveloped in a common cutaneous covering, on which rudiments of nails are sometimes present. No trace of hind limbs in existing forms. External surface covered with a tough, finely wrinkled, or very rugose skin, naked, or with fine hairs sparsely scattered over it.

The skeleton is remarkable for the massiveness and density of most of the bones of which it is composed, especially the skull and ribs, which must add to the specific gravity of these slow-moving animals, and aid in keeping them to the bottom of the shallow waters in which they dwell, while feeding on aquatic vegetables. The skull presents many peculiarities, among which may be indicated the large size and backward position of the anterior narial aperture, a further modification of that met with in the Tapirs among Ungulates, and presenting some approach to that so characteristic of the Cetacea. The nasal bones are generally absent in the recent forms,