Cambridge Natural History Mammalia/Chapter VIII

by Frank E. Beddard

CHAPTER VIII

EDENTATA—GANODONTA

Order II. EDENTATA

Terrestrial, partly subterranean, or arboreal creatures of quite small to gigantic size (some extinct genera), with frequently a covering of scales or bony scutes. Limbs clawed. Teeth either totally absent or, if present, imperfect in structure, being without enamel, and not forming a complete series; incisors and canines being as a rule absent. Teats axillary, pectoral, or inguinal.^[1] Retia mirabilia very common in the extremities.

To this group the name of Bruta was given by Linnaeus, but then it included not only the families which we now place in the modern order Edentata, but also the Elephant and the genus Trichechus. Mr. Thomas has proposed to change the name into Paratheria, which name is suggestive of what he and some others think concerning the systematic position of the group, i.e. that it is not to be placed in the Eutherian group of mammals at all, but represents a separate twig which has arisen with the Eutheria from a low mammalian stock. This view can hardly be accepted if the Ganodonta—which will be treated of presently—be really ancestral Edentates, for they are not in any way a Prototherian mammalian group, so far as their remains enable us to judge.

The Edentata contain the Sloths, Ant-bears, Armadillos, Manis and Orycteropus, among living forms. The great Ground-Sloths, Megatherium, etc., and Armadillos, Glyptodon, etc., represent the extinct forms.

The name that has been applied to this group is inappropriate inasmuch as many Edentates have teeth. It is, however, by a number of small tooth-characters that the order can be defined. Thus if teeth are present they are simple in structure, without enamel in the adult condition, though a rudimentary enamel-organ has been discovered in an Armadillo. The teeth, moreover, are not found in the anterior part of the mouth, and they grow from persistent pulps; neither is there much differentiation among them. It is not possible, however, to speak of the Edentates as quite homodont, since in Orycteropus there are large cheek-teeth; but there is at any rate not a marked heterodonty in that or in any other Edentate. It used to be said that the Edentates were monophyodont. But the Armadillo Tatusia was subsequently found to possess a second suppressed dentition, and after this discovery Mr. Thomas proved that Orycteropus is also diphyodont. Since then other Armadillos have been shown to be diphyodont; and the whole group therefore, so far as concerns those members that have teeth, may in all probability be regarded as typically mammalian in this respect.

These characters are slender enough, but there seem to be no others by means of which the members of this order can be satisfactorily linked together. The fact is, that we have here a polymorphic order which contains in all probability representatives of at least two separate orders. We have at present a very few, and these perhaps highly modified, descendants of a large and diverse group of mammals. For convenience' sake they will be all treated of under the head of Edentata.

Although for the probable reasons already stated it is a hard matter to frame such a definition as will include all existing Edentates, it is easy enough to define two groups in this heterogeneous order; to define one group we should say, rather, and then to regard the leavings as forming another not so easily definable a group.

The perfectly-definable group is that which includes the American Anteaters, the Armadillos, and the Sloths. In all these creatures, which may certainly be regarded as representing on their own account as many family types, there are a number of important and highly-characteristic anatomical features which they share in common. So exceedingly different are these three types in general appearance and (correlated with that) in way of life that these common characters acquire increased importance.

Fig. 89.—Great Anteater (Myrmecophaga jubata). A, Side view of twelfth and thirteenth thoracic vertebrae. B, Posterior surface of second lumbar vertebra. C, Anterior surface of third lumbar vertebra, × ⅔. az, Anterior zygapophysis; az¹, az², az³, additional anterior, articular facets; cc, facet for capitulum of rib; m, metapophysis; pz, posterior zygapophysis; pz¹, pz², pz³, additional posterior articular facets; t, transverse process; tc, facet for articulation of tubercle of rib. (From Flower's Osteology.)

The first of these characters is the series of additional zygapophyses on the posterior dorsal and lumbar vertebrae; these are very clear in the Anteaters and Armadillos; less clear, but still obviously represented, in the Sloths. In the second place, they all possess a clavicle, rudimentary, it is true, in the Great Ant-bear, but still present. Thirdly, the testes are abdominal throughout life, a character which they share with such lowly-organised animals as the Monotremata and the Whales. Finally, and this is by no means a matter to be overlooked, not only are all the existing members of this group American in range, but there is no evidence to prove that they have ever existed elsewhere. No European or Old-World representatives have as yet been discovered which can be referred to the Anteater, Armadillo, or Sloth type with certainty.^[2]

Of these American forms, which will be treated of first, the Armadillos are further apart from either Sloths or Anteaters than the last two are from each other. The name Xenarthra has been suggested for the American Edentates with "abnormal" vertebral articulations; the corresponding Nomarthra includes the Old-World forms.

Fig. 90.—Right scapula and clavicle of Two-toed Sloth (Choloepus hoffmanni). × 1⅔. a, Acromion; af, prescapular fossa; c, coracoid; cl, clavicle; csf, coraco-scapular foramen; gc, glenoid cavity; pf, postscapular fossa. (From Flower's Osteology.)

Between the Sloths and Anteaters the extinct Megatherium and some of its allies are to a certain extent intermediate. But it may be pointed out in the first place that there are certain important resemblances between the living forms. In both, retia mirabilia are developed in the tail (in spite of its reduction in the Sloths) and in the limbs. But, as is well known, retia are also found in other mammals far removed in the series from these under consideration. The reproductive organs generally are very similar, and they have both a dome-shaped and deciduate placenta. The latter character they share with the Armadillos and with the Aard Vark; Manis having a non-deciduate placenta which is, like that of the Carnivora, zonary in form. The Edentates, at any rate the American forms, have a double vena cava posterior and no azygos vein. This condition is also met with among Whales.

Osteologically the Sloths and Anteaters are united by the fact that the coracoid becomes fused with the coracoid border of the scapula, thus forming a foramen; the importance of this character is, however, discounted by its occurrence in three genera of Cebidae.

The above facts embody the views of Sir William Flower.^[3] A subsequent study of the brain and of the muscles of these animals has led to results not entirely in harmony with these views.

Dr. Elliot Smith is of opinion,^[4] after an exhaustive study of the Edentate brain, that in this region of the body the present group shows very decided points of likeness to the Carnivora; that is, so far as concerns the Anteaters. On the other hand, Orycteropus is as distinctly comparable with a primitive Ungulate type, such as is exemplified by Moschus. "If the brain of Orycteropus," he remarks, "were given to an anatomist acquainted with all the other variations of the mammalian type of brain, there is probably only one feature which would lead him to hesitate in describing it as an exceedingly simple Ungulate brain. That one feature is the high degree of macrosmatism.^[5] Manis, on the other hand, does not come especially near to Orycteropus. The brain of Manis conforms to a simple type of architecture, which agrees in many points with both those of Orycteropus and the American Edentates; there is not sufficient evidence to show which type it really favours." Elliot Smith would, in fact, agree with Max Weber that it is better, if a division is to be made, to divide the group into three orders:—the Xenarthra (Sloths, Anteaters, and Armadillos), Tubulidentata (Orycteropus), and Squamata (Manis), instead of into Xenarthra and Nomarthra.

Messrs. Windle and Parsons^[6] are disposed to see in muscular similarities reasons for uniting Manis with the American Edentates, though they confess to being unable to place Orycteropus; in this animal, they say, "we are more struck by the generalised mammalian arrangement of its muscles than by any special Edentate characters. There are, however, two muscles in Orycteropus which show peculiarities not found elsewhere than in the Edentates";—the triceps, which has more than one scapular head, and the tibialis posticus, which is double. They conclude that Orycteropus "presents some feeble claims to be taken into the order."

We shall here adopt the following divisions.

Sub-Order 1. XENARTHRA.

Fam. 1. Myrmecophagidae.—The family Myrmecophagidae contains three genera, all South American in range. These genera, Myrmecophaga, Tamandua, and Cycloturus, agree greatly in their outward form. They are all without teeth, and have long snouts and long protrusible tongues. The fur is thick, and they have powerful claws wherewith to break down the strong ant-hills upon whose inhabitants they feed. Tamandua and Cycloturus are arboreal, Myrmecophaga is terrestrial in habit. The claws of the arboreal forms are useful to destroy the bark, and thus bring to light insects which lurk in such situations.

Fig. 91.—Great Anteater. Myrmecophaga jubata. × ¹⁄₁₀.

The genus Myrmecophaga contains but one species, the Great Anteater, Myrmecophaga jubata. It is a large and handsome animal, with long, shaggy, greyish-black hair and a broad white stripe across the shoulder. The coloration is similar in the two sexes. Including the long and bushy tail it reaches a length of over 7 feet. It is on account of its long tongue and greatly developed salivary glands that this and the allied genera were originally placed with Manis. It is the submaxillary glands which are so enormous; they extend back over the chest, and open by three distinct ducts, of which two unite just before the external orifice. Along their course these ducts are provided with a sphincter muscle, which squeezes the secretion towards the external orifice into the mouth-cavity. The stomach is somewhat gizzard-like. The intestine has no caecum.^[7]

The Anteater's great claws are not only serviceable in tearing up the ground to get at its food; armed with them he does not fear, as Mr. Waterton remarked, "the fatal pressure of the serpent's fold or the teeth of the famished jaguar." An Anteater, too, is more than a match for a big dog, and will rip open its belly with the claws while the dog is vainly trying to make an impression with its teeth upon the shaggy hair.

Tamandua is a smaller animal than Myrmecophaga, and, as has been stated, is arboreal; associated with this habit is a prehensile tail. Like the last genus, Tamandua has a rudimentary clavicle, this bone being well developed in the little Cycloturus.

Fig. 92.—Skull of Anteater (Myrmecophaga). Lateral view, al.sph, Alisphenoid; cond, condyle of mandible; cor, coronoid process of mandible; ex.oc, exoccipital; ext.aud, external auditory meatus; fr, frontal; ju, jugal; lcr, lachrymal; max, maxilla; nas, nasal; occ.cond, occipital condyle; pal, palatine; par, parietal; p.max, premaxilla; s.oc, supraoccipital; sq, squamosal; ty, tympanic. (From Parker and Haswell's Zoology).

The skull of the Anteater^[8] is very long and low; the fore-part is tubular, and there appear to be no traces of teeth. The premaxilla is very small; the zygomatic arch is imperfect, and does not reach the squamosal behind. A curious feature of this genus, which it shares with some Dolphins and other Whales, is that the pterygoid bones develop palatine plates which meet each other in the middle line, and thus shift the opening of the posterior nares backwards. This is also, of course, a character of various lower vertebrates. Another Whale-like character in the skull is the weak character of the mandible, which does not give off a marked coronoid process. But then in neither group is there much mastication. The tympanic, periotic and squamosal are ankylosed together. A peculiarity of the cervical vertebrae is that (as in the Camels) the vertebrarterial canal of several of the vertebrae perforates the pedicle obliquely. There are fifteen or sixteen dorsal and three or two lumbar vertebrae. The additional zygapophyses upon the former have been already referred to. The mode of articulation of the ribs is highly singular.

Fig. 93.—Skull of Anteater (Myrmecophaga). Ventral view. Letters as in Fig. 92. In addition, b.oc, basioccipital; glen, glenoid surface for mandible; pter, pterygoid. (From Parker and Haswell's Zoology.)

Fig. 94.—Side view of three mesosternal segments of a young Anteater (Tamandua), showing the mode of articulation of the sternal rib (sr). mst, The upper or inner surface of the mesosternal segment; sy, the synovial articulation between the segments. (From Flower's Osteology, after Parker.)

Each segment of the sternum (of which there are eight) is separated from the next by a synovial membrane: and it has on either side two facets for articulation with the ribs. The way in which these latter bones are connected with the sternum is curiously like their mode of connexion with the spinal column at their other end. With this may be possibly compared the double articulation of the single rib (which articulates with the sternum) in the Rorquals. In Cycloturus this mode of articulation does not occur.

The manus of Myrmecophaga is five-fingered. Of these the third digit (as in Perissodactyles) is the most prominent; it is at least double the width of the second or third finger; the pollex is very slender. In the little Cycloturus this is carried to a greater extent: the third digit is relatively enormous; the first and the fourth have become quite rudimentary; while the fifth is only just recognisable as a minute ossification.

Fig. 95.—A, Manus of Great Anteater (Myrmecophaga jubata). × ⅓. B, Manus of Little Anteater (Cycloturus didactylus). × 2. c, Cuneiform; l, lunar; m, magnum; p, pisiform; s, scaphoid; td, trapezoid; tm, trapezium; u, unciform; I-V, digits. (From Flower's Osteology.)

The chevron-bones in the tail surround a well-developed rete mirabile, a rete being found in precisely the same position in the Eastern Manis. Tamandua has also retia, which are also found in the Spider-monkeys.

Cycloturus is by far the smallest of the Anteaters. It has only two toes on the fore-feet. It is to be distinguished, anatomically, from its larger relatives by the complete clavicle, and by the fact that the pterygoids do not meet in the middle line of the skull. The ribs, too, are unusually wide, as in the Whale Neobalaena, and form a bony encasement for the body. It has two small caeca. Of fossil Anteaters but little is known. The most interesting form is Scotaeops, interesting because it has two small back teeth, which are totally lost in its living allies. The huge Patagonian extinct bird Phororhacos, first known by a lower jaw, was at one time regarded as a member of this group on account of the form and edentulous character of the jaw.

Fig. 96.—Unau, or Two-toed Sloth. Choloepus didactylus. × ¹⁄₅. (After Vogt and Specht.)

Fam. 2. Bradypodidae.—The Sloths, genera Bradypus and Choloepus, come, as already stated, very near to the Anteaters, in spite of their striking difference in appearance. The Sloths are purely arboreal creatures, with strong recurved claws, which serve as hooks to keep them suspended from the lower side of a branch. The three-toed sloth, Bradypus (or "Ai"), has the exceptional number of nine cervical vertebrae; the two-toed sloth, Choloepus hoffmanni (or "Unau"), has the equally exceptional number of six. The hair is long and shaggy, and gets an adventitious green colour from the presence of minute algae.^[9] This gives to the animal the appearance of a lichen-covered bough, a resemblance which is increased in one species by an oval mark upon the back, which suggests forcibly a broken end of such a branch. The likeness of a Sloth to its surroundings is pointed out by

Fig. 97.—Skull of Three-toed Sloth. Bradypus tridactylus. Lateral view. fr, Frontal; ju, jugal; lcr, lachrymal; max, maxilla; nas, nasal; par, parietal; s.oc, supra-occipital; ty, tympanic. (From Parker and Haswell's Zoology.)

Dr. Siemann,^[10] who observed that a species occurring in Nicaragua "has almost exactly the same greyish-green colour as Tillandsia usneoides, the so-called 'Vegetable Horsehair' common in the district.... If it could be shown that it frequented trees covered with that plant ... there would be a curious case of mimicry between the sloth's hair and the Tillandsia, and a good reason why so few of these Sloths are seen." The stomach in the Sloths is complicated in structure, with several chambers; one of these gives off a long crescent-shaped caecum. The skull of the Sloths agrees in a number of particulars with that of the Anteaters.

Fig. 98.—Skeleton of Three-toed Sloth. Bradypus tridactylus. (After de Blainville.)

The zygoma is incomplete, though the part connected with the frontal has a strong downward process like that found in Diprotodon and some other mammals. There is, moreover, a process from the squamosal, though it does not reach the anterior part and thus complete the arcade. The premaxillaries are very small, and are usually lost in dried skulls. Coupled with these points of likeness are some differences. The lower jaw, for instance, has a well-marked coronoid process. The pterygoids do not meet in the middle line. The teeth are five or four in each half of each jaw. There is no trace of a second set.

A peculiarity of the Sloths is the enormous number of dorsal vertebrae. There are twenty-three of these in Choloepus hoffmanni, but only fifteen to seventeen in the Three-toed Sloth, Bradypus. As in other American Edentates, the acromion joins the coracoid. This connexion occurs in both the Two-toed and the Three-toed species. The limbs of these creatures are very long, a concomitant of an arboreal life. The femur has no third trochanter. The genus Bradypus, which by reason of the fact that it has not lost the third toe on the manus seems to be more primitive than Choloepus, shows another structural feature which does not bear out this conclusion. The trapezoid and the os magnum of the carpus are united, while in Choloepus they are perfectly distinct bones.

The intestine has no caecum.

There are several species of Sloths. Eminently perfect though the organisation of the Sloth in relation to its particular surroundings appears to us, Buffon selected the animal as the very type of imperfection in nature. "One more defect," he wrote, "they could not have existed."

Fam. 3. Dasypodidae.—The family Dasypodidae or Armadillos contains a considerable number of genera. Tatusia, Tolypeutes, Dasypus, Xenurus, Priodon,^[11] and Chlamydophorus. They have all a more or less rigid covering of bony plates imbedded in the skin, which are not in the least comparable with the scales of the Manis. Save the Whales, in one or two genera of which traces of a dermal armature exist, the Armadillos are unique among existing mammals in this particular. The term "Edentate" is especially inapplicable to the Armadillos; the genus Priodon may have more than forty teeth in each jaw; a total of ninety was found in one specimen examined by Professor Kükenthal. In the tendency of the teeth to multiply, we have another example of a state of affairs which characterises so many Whales. Generally, however, seven to nine is the number of teeth in each half jaw, of which one is often implanted in the premaxilla. The Armadillos show their alliance with the other American Edentates in the points enumerated above. Their teeth specially ally them to the Sloths, while the salivary and digestive organs generally are on the Anteater plan, but present a less extreme development. There are, however, caeca, paired as in birds, in the genera Dasypus and Chlamydophorus. The others have none. But there is a dilatation at the commencement of the large intestine, which is not very different from the slightly-developed caeca of Dasypus.

There are certain peculiarities in the skeleton, which distinguish this family.

Fig. 99.—Skull of Armadillo. Dasypus sexcinctus. × ⅔. ex.oc, Exoccipital; fr, frontal; max, maxilla; nas, nasal; par, parietal; peri, periotic; p.max, premaxilla; s.oc, supraoccipital; sq, squamosal; ty, tympanic. (From Parker and Haswell's Zoology.)

The skull in the Armadillos presents a number of likenesses to the other American Edentates.^[12] The premaxillaries are small, but are larger in Dasypus than in Tatusia. On the other hand the lachrymals are larger in the latter. The zygomatic arch is complete, but there is no downward process as in the Sloths. In Tatusia (but not in Dasypus) the "short thick pterygoids add somewhat to the hard palate." This is clearly a beginning or a remnant of the quite crocodilian character of the palate of Myrmecophaga. In the cervical vertebrae we see the Whale-like character of fusion between individual vertebrae; and also, as in the Whales, the degree to which this fusion is carried out varies; two to four may be thus united. The additional articular facets upon the dorsal vertebrae have been already commented upon as a point of important likeness to other American Edentates. The dorsal vertebrae are commonly eleven in number, the lumbar being three. But in Priodon the numbers are twelve and two respectively. There are traces to be observed of the double-headed attachment of the ribs to the sternum. The

Fig. 100.—Bones of the right manus of the Hairy Armadillo. Dasypus villosus. × ⅔. c, Cuneiform; l, lunar; m, magnum; p, pisiform; R, radius; s, scaphoid; td, trapezoid; tm, trapezium; u, unciform; U, ulna; I-V, digits. (From Flower's Osteology.)	Fig. 101.—Bones of the manus of the Great Armadillo. Priodon giganteus. × ⅓. a, An accessory carpal ossicle in front of the pisiform, which is not seen in the figure. Other letters as in Fig. 100. (From Flower's Osteology.)

shoulder girdle of the Armadillos is somewhat diverse in form in different genera; the acromion is always large, and is remarkable in Priodon for the fact that the humerus also articulates with it, its extremity being recurved, and forming a socket for this purpose. As in some other Edentates there is a second spine on the scapula behind the first. The clavicle is strong. There is some variation in the form of the manus. It is five-fingered in Dasypus; in Tolypeutes the first digit has vanished; on the other hand, in Priodon, the fifth has become rudimentary and the third enormously enlarged. This latter fact recalls the arrangement characteristic of Myrmecophaga. The pelvis is greatly attached by the ischium to the vertebral column. The femur has a third trochanter.

The various forms of Armadillos are largely distinguished by the number of movable thin bands of scutes lying between the large anterior and posterior shields. Thus we have Dasypus sexcinctus, Tolypeutes tricinctus, etc.

Fig. 102.—Pelvis and sacrum of Armadillo. Dasypus sexcinctus. ac, Acetabulum; il, ilium; isch, ischium; obt.for, obturator-foramen; pect.tub, pectineal tubercle; pub, pubis. (From Parker and Haswell's Zoology.)

The little Pichi-chago (or, more correctly, Pichy-ciego), Chlamydophorus, which only grows to about 5 inches in length, has no movable bands at all. It is covered with a uniform series of plates, which, moreover, are not discontinuous at the neck. It differs, too, from the prevailing Armadillo-type by the absence of conspicuous external ears. In the anterior part of the body the armature consists of little more than the horny plates, which in other Armadillos overlie the bony dermal plates. In the hinder region the bony plates are strong. In this animal, therefore, we have the dermal armature reduced to a minimum; but it must be noticed that, like the extinct Glyptodons, the armature is continuous and nowhere ringed.

The genus Tolypeutes, of which the best-known species is T. tricinctus, the Apar (there are two other species in the genus), can roll itself up into a ball like the Pill-Millipede (Glomeris), and, protected by its armour, roll away from its enemies like the Arthropod under similar circumstances. This mode of protection, be it observed, is also adopted by the Pangolin and by the Hedgehog. The genus has only three movable bands. The tail is short, and is covered with large tubercles. This genus is very markedly digitigrade when running.

Fig. 103.—Three-banded Armadillo or Apar. Tolypeutes tricinctus. × ¼.

Fig. 104.—Peludo Armadillo. Dasypus sexcinctus. × ¼. (After Vogt and Specht.)

The Peludo, Dasypus sexcinctus, is, like other Armadillos, an omnivorous creature, and appears to be particularly fond of carrion. It will burrow up to a decaying carcase like the ground-beetles. Mr. W. H. Hudson has described the way in which this Armadillo will kill a snake by holding it down and literally sawing the reptile in half by help of the sharp and serrated edges of the carapace. Dasypus has a very short tail, which is shielded by distinct rings near the base.

Tatusia novemcincta is a species with nine movable bands. The genus has four teats; the ears are near together. There are no caeca and no azygos lobe to the lung. A species apparently belonging to this genus, but described under the generic names of Cryptophractus and Praopus, is remarkable for the thick covering of hair, not entirely wanting but usually thin in other Armadillos. In this particular species the coat of hair is so thick as to conceal the underlying plates of the carapace. The individual hairs are stiff, and one inch and a half in length.^[13]

The genus Xenurus contains several species, the best known of which is inaptly named X. unicinctus. As a matter of fact the characteristic feature of the genus is the existence of twelve or thirteen movable plates between the two ends of the body. X. unicinctus has twelve dorsal and three lumbar vertebrae. This Armadillo, known by the vernacular name of the Cabassou, has one of the most modified hands that are found in the family. The first two digits are slender and elongated; but are quite normal in the number of their phalanges. In the remaining three digits the metacarpal is short and broad, while the proximal phalanx is either suppressed altogether or fused with the metacarpal, the middle phalanx is present but short, while the third phalanx is very large indeed. As in Dasypus, but not as in Tatusia, which is in so many other respects divergent from these genera, the lungs have an azygos lobe. As a small point of difference, tending to show an alliance between the genera Xenurus and Dasypus and their difference from Tatusia, is the deeply-imbedded gall-bladder; this sac is not nearly so deeply plunged into the hepatic tissue in Tatusia. Xenurus has no caecal dilatations. The brain "is intermediate in its form and surface markings between Dasypus and Tolypeutes." The small intestine is nearly eighteen times the length of the large. But these intestinal measurements are not of much avail in this group as marks of affinity, since in three species of Dasypus Garrod gives the following widely-divergent lengths:—D. villosus, 11.5 feet and 1.25; D. minutus 5.1, with a large intestine of no less than 7 feet; D. vellerosus 4.3 and .66.

Priodon is the giant of its race. This Armadillo may reach a length of 3 feet to the base of the tail. The tail is some 20 inches long. The large number of teeth has been already noticed. There are twelve or thirteen bands. Other points in the structure of this genus have already been mentioned, and need not be recapitulated. This Armadillo feeds upon termites and carrion.

Scleropleura is unfortunately but imperfectly known. The single species, named by Milne-Edwards^[14] S. bruneti, is apparently a very rare inhabitant of Brazil. It is known by a single skin, which was tanned by the hunter who obtained it. Thus the hair, if any, has dropped out. The plates in the skin are deficient along the back and even upon the top of the head, and are barely represented upon the tail posteriorly. The ears are small and distant from each other. The tail is longish, about one-third of the length of the body. The total length of the creature including the tail is rather more than a foot and a half. The hunter who obtained it regarded it as a hybrid between an Armadillo and an Anteater.

Extinct Xenarthra.—There are a good many extinct forms of Armadillo, apart of course from the Glyptodons. Peltephilus is referred to later (p. 186). Dasypus was represented by a large form, 6 feet long, with a skull of one foot in length. The genus Eutatus was also large. The carapace was formed of thirty-three distinct bands, of which the last twelve are soldered together, but not fused into a shield as in Dasypus, etc.

An extinct group of American Edentates, termed the Gravigrada,^[15] are somewhat intermediate between the Sloths and the Anteaters. A number of the genera are well known from complete skeletons.

One of the typical forms of this group is Mylodon, which, together with its immediate allies, is often placed in a separate family, Mylodontidae.

Mylodon itself was a large creature, as big as a Rhinoceros. It was covered externally by armour in the skin, which did not form a massive armature as in the Glyptodonts, but was in the form of scattered plates, small and not fused together. The general aspect of the skull is decidedly Sloth-like. As in that animal, the malar bone is bifid posteriorly, and between the bifurcation is embraced the process of the squamosal. This latter is thus more developed than in the Sloth, but there is no actual union between it and the malar. The premaxilla is small. The lower jaw has both coronoid and ascending processes, and is massive. There are five teeth on each side above, and four on each side below, as in the Sloths. There are the normal seven cervical vertebrae and sixteen dorsals. The limbs are not long and slender,but short and strong, the animal having been terrestrial. The fore-feet were five-toed, of which the three inner toes had claws. The hind-feet were only four-toed, and the two inner only were clawed.

Fig. 105.—Mylodon robustus. (Restoration, after Owen.)

Scelidotherium is a genus which is a trifle smaller than the last. It has only four properly-developed toes in the fore-foot, the thumb being rudimentary; of these, the first two bear claws. The hind-feet are also four-toed. Like Mylodon, Scelidotherium is a Pleistocene genus.

Glossotherium has a skull very much like the last two genera; but it is remarkable for the fact that the nostrils instead of being unprotected with bone anteriorly are there closed by a plate of bone formed by the well-developed premaxillae, the nostrils appearing at the sides, and giving the skull a curious likeness to that of a Chelonian. From a series of recent and most important observations it appears to be clear that this genus has survived into quite modern times.^[16]

The well-known naturalist of La Plata, Señor Moreno, engaged in studies connected with the political boundary line between Chili and the Argentine, had occasion to visit Consuelo Cove on Last Hope Inlet in Patagonia. Hanging from a tree he noticed a piece of dried skin, which at once struck him as looking more like the remains of a Mylodon than of any living animal. The inhabitants regarded this piece of skin as a great curiosity, but were of opinion that it was the hide of a cow encrusted with pebbles! This fragment from a bygone age was originally described by Professor Ameghino, who had apparently seen some of the bonelets imbedded in it, as Neomylodon listai, "a living representative of the ancient Gravigrade Edentates of Argentina." That this piece of skin is of quite recent date seems to be proved by a number of considerations. In the first place it is covered by long hair of a light yellowish-brown colour; it does not seem likely that hair would preserve its character for geological epochs. The nearest corresponding case is that of the remains of Moas in New Zealand, whose feathers, dried skin, and tendons are known. Now the Moa was unquestionably contemporaneous with man, as abundant surviving legends prove, and indeed it cannot have been long extinct. Still, hair is a resisting structure, and in a dry cave, with no possibility of irruptions of floods, might retain its characters for long periods. The evidence, however, of more recent date is stronger than this. The skin shows patches of reddish colour, suggestive of course of blood-stains. A small piece of the outside of the skin at the cut edge, which presented the appearance of freshly or comparatively freshly dried fluid, was submitted to a chemical examination and shown to be serum! Dr. Lönnberg examined chemically a bit of the skin itself and found in it, after boiling, glue, "which proves that the collagen and gelatinous substances are perfectly preserved." After this it seems impossible to suppose that the skin can be of any very great age; for bacteria would have finished their work upon the serum and gelatine long ago. Combined with the fresh appearance of the skin is the very fresh appearance of the skull. In fact it is impossible to believe that the animal was not alive quite a few years since, relatively speaking. It is admitted that this animal was contemporaneous with man. There are actually legends of a creature which may have been this Glossotherium. "Ancient chroniclers inform us that the indigenous inhabitants recorded the existence of a strange, huge, ugly monster, which had its abode in the Cordillera to the south of latitude 37. The Tehuelches and the Gennakens have mentioned similar animals to me, of whose existence their ancestors had transmitted the remembrance; and in the neighbourhood of Rio Negro, the aged Cacique Sinchel, in 1875, pointed out to me a cave, the supposed lair of one of these monsters, called 'Ellengassen'; but I must add that none of the many Indians with whom I have conversed in Patagonia have ever referred to the actual existence of animals to which we can attribute the skin in question."

A rude painting in a cavern, in red ochre, seems to Dr. Moreno (whose words we have just quoted) to be somewhat suggestive of a Glyptodon. There are some reasons for believing that this quadruped was kept by man as a domestic creature. In the cave are two walls of rough pieces of stone which seem to have dropped down owing to the wearing away of the roof; they also seem to have been loosely piled together to form two walls, within which enclosure an imperfect skull of the animal was found. This skull shows clearly that the so-called "Neomylodon" must be referred to Glossotherium or Grypotherium, as it is sometimes termed. This skull is perforated on the roof in such a way as could only have been effected (in the opinion of experts) by a weapon in the hand of a man. A hole in the skin has been even compared to a bullet-wound. But this it is perhaps unnecessary to discuss. The skin of Glossotherium is, like that of other extinct "Ground-sloths" (e.g. Mylodon), filled with small and irregular ossicles. But in Mylodon, the sculptured appearance of the dermal ossicles appears to indicate that they reached the surface of the body and were covered by epidermis alone, which is not the case with the animal now under consideration. The microscopic characters of the ossicles, too, show differences in the two. Glossotherium being "precisely intermediate between Mylodon and the existing Armadillo (Dasypus)." Now Glossotherium and Mylodon are regarded as forms which lie between the existing Anteaters and the Sloths of the same part of the world. We have already pointed out the facts of structure which lead to this conclusion. It might therefore be reasonably surmised that the hair of Glossotherium would be also intermediate, or at least like that of one of the two genera Myrmecophaga and Bradypus. But microscopical investigation has negatived this supposition. It has shown that the Armadillos are in this matter the nearest relatives of Glossotherium. This result is important as tending further to confirm the close interrelationship of all the American Edentates as contrasted with the Old-World forms—a matter which has already been emphasised. It is suggested, however, that the absence of under fur, which is so well developed in the Sloth, and the difference shown in transverse sections from the hair of Myrmecophaga, may be explained by difference in habitat. Glossotherium lived under conditions similar to those under which the Armadillos live to-day. Thus the outer covering of the body became alike in the two cases, the same needs supervening in both genera.

Lestodon is another allied genus, which seems to possess canines. At any rate, in front of the four molars, and separated from them by a diastema, is a smallish, somewhat canine-like tooth, in both jaws.

Megalonyx and its allies are sometimes placed in a distinct family, Megalonychidae. Megalonyx itself had a skull very like that of Bradypus, being shorter and not so elongated as in the Mylodontidae. There is a strong tusk anteriorly, which is separated by a considerable space from the three molars lying behind it. Both pairs of limbs seem to have possessed five toes. This is a North American genus. It differs from the bulk of the American Edentates in having a complete jugal arch.

Megatherium is the type of yet a third family, Megatheriidae, of the Gravigrade Edentates. This creature is familiar from the many restorations which have been built up, and from its huge bulk, little short of that of an elephant. The skull, which is small for the size of the creature, has a complete jugal arch, from the middle of which depends a downward process as in other allied forms. The teeth grow to an extraordinary depth, and there are five of them in the upper and four in the lower jaw—on each side of course. The fore-limbs of the Megatherium are very much more slender than the enormously bulky hind-limbs, upon which and the equally massive tail the animal seems to have supported itself while tearing down branches of trees, upon whose leaves it fed. In the scapula the acromion joins the coracoid as in Bradypus; the clavicle is large. The fore-limb is four-toed, and the hind-limb three-toed. The latter has but one clawed digit (the third, i.e. the inner). On the manus, the three inner digits have powerful claws. This animal, too, was Pleistocene in time. The Megatheriidae had, however, small as well as gigantic forms.

The genus Zamicrus had a skull no bigger than that of a Sloth, while Nothrotherium was also a comparatively small creature; the teeth of the latter genus are reduced to 4/3.

The extinct group of the Glyptodontidae comprises large creatures with a dense covering of bony scutes which are arranged in a tesselated fashion, and thus form an immobile armature of immense strength. In correspondence with this massive carapace the dorsal vertebrae have fused together, and the lumbar vertebrae form a series ankylosed to each other and to the following sacrals. These creatures are all South American.

Fig. 106.—Glyptodon clavipes. × ¹⁄₁₂. (After Owen.)

Glyptodon, the genus which gives its name to the family, is known from numerous remains in South America, and also from so far north as Texas and Mexico. It grew to be as long as 16 or 17 feet. In the skull there is an exceedingly long downward process of the zygomatic arch, as in Sloths, the arch itself being complete. The process extends so far down as to reach a point about on a level with the middle of the lower jaw. The nasals are short or rudimentary. As in Myrmecophaga, the pterygoids enter into the formation of the bony palate. The lower jaw has a spout-shaped extremity, and, behind, it rises into an enormous vertical branch as high as the front part of the jaw is long. There are eight teeth in each half of each jaw. As in some Armadillos, the cervical vertebrae are at least partly fused. The atlas is free, but the rest, or at any rate five of them, are united. The last cervical is sometimes fused with the succeeding dorsals; the latter are twelve in number, and are fused together so far as concerns their centra and neural processes. The succeeding region of the vertebral column includes seven to nine lumbars, which are fused with the eight sacrals; in this region the neural processes are high, and there is thus produced a strong and lofty ridge along the back, which forms a powerful support for the carapace. The fore-limbs are shorter than the hind-limbs, which latter are attached to an unusually massive pelvis. The claws of the limbs are blunt and almost hoof-like.

The heavy carapace consists of sculptured, five or six-sided plates, which have no particular arrangement in the middle, but towards the margins show indications of an arrangement in transverse rows. The moderately long tail is also encircled by bony skin-plates which are thorny above, or at least provided each with a blunt upstanding process. It appears that outside this bony system of scutes were horny epidermic scales, corresponding exactly with the tesserae which they cover. There are apparently a good many species of Glyptodon.

In the allied genus Panochthus the tail is rather longer, and the bony rings which surround it, instead of being all movable as in Glyptodon, are at first so, but later, i.e. towards the end of the tail, become welded into a single and massive piece. Both feet are here four-toed, while in Glyptodon the hind-feet are five-toed and the fore-feet four-toed.

Daedicurus shows a further specialisation, in that the feet have three and four digits respectively. The orbit too shows a specialisation in being separated from the temporal fossa. The descending process of the zygomatic arch is not so extraordinarily exaggerated as it is in Glyptodon. It has the same terminal tube of osseous scutes upon the tail. This creature seems to have reached a length of about twelve feet.

Propalaeohoplophorus is, unlike the great Armadillos that we have hitherto dealt with, a small animal, not exceeding 2 feet or so in length of carapace. A small alveolus on each side of the premaxillae seems to suggest the former presence of an incisor tooth; and it seems that the animal possesses both true molars and premolars; for the first four of the eight teeth are much simpler in structure than those which follow. The dorsal vertebrae again are not fused together; the hind-limbs are five-toed. All the plates of the carapace are arranged in definite transverse rows; it has been observed, too, that some of the anterior scutes overlap like those of the Armadillos, to which this animal possesses further likenesses in the exclusion of the maxillae from the border of the nostril (a Glyptodont character), and the comparative feebleness of the scutes.

A primitive genus also appears to be Peltephilus, which is perhaps rather an Armadillo than a Glyptodon. However, it comes somewhat between the two, like Propalaeohoplophorus, with which it may therefore be treated. A most singular feature of this genus has been mentioned on p. 27 in connexion with the skull in the Mammalia generally. That is the fact that a portion of the squamosal surrounding the articular facet for the lower jaw is separated by a suture from the rest of that bone, and is therefore obviously suggestive of the quadrate in the lower Vertebrates. As in certain Armadillos and Glyptodons, etc., the pterygoids appear in this genus to have taken a share in the formation of the hard palate. The plates of the carapace were movable, as is shown by the fact that they sometimes slightly overlap. In view of the possible origin of the Edentates from lowly-organised Mammalia, it is noteworthy that the humerus has been especially compared to that of the Monotreme. Peltephilus differs from other Armadillos in having teeth in the front of the jaws. The total number of teeth is twenty-eight, i.e. seven in each half of each jaw.

Sub-Order 2. NOMARTHRA.

As already explained, the Old-World Edentates differ from the New-World forms in having normal dorsal vertebrae, that is to say, without additional zygapophyses. That negative feature, however, though combined with the positive fact that both the Old-World forms feed upon ants, is hardly sufficient to outweigh the many structural differences which distinguish the Orycteropodidae from the Manidae; which will be placed therefore in different groups. To that containing the Aard Vark, the name Tubulidentata may be applied.

This group contains but one family, the Orycteropodidae, of which there is but a single genus.

The Aard Vark (earth-pig), genus Orycteropus, is characterised by its heavy build, the body being covered by rather coarse and not very abundant hair; the snout is long and pig-like, with round nostrils at its end; the ears are long, erect, and pointed; the tail is very thick at first, so that it has been aptly described as "a tapering of the body to a point." The fore-limbs are four-toed, the hind five-toed.

Fig. 107.—Aard Vark, or Cape Anteater. Orycteropus capensis. × ¹⁄₁₆.

In the skull there is a complete though slender zygoma; the premaxillaries, though small, are not so rudimentary as in the American Edentates. The annular tympanic is not ankylosed to the surrounding bones, a character found in other low mammals. Contrary to what is found in Manis, Orycteropus has a huge lachrymal. There are thirteen dorsal and seven lumbar vertebrae. The clavicle is well developed. Orycteropus is peculiar among Edentates in that the ischia do not unite with the vertebral column. The femur has a third trochanter.

As mentioned on p. 162, the Aard Vark is diphyodont like normal mammals. The permanent teeth consist of five molars and premolars on each side of each jaw; the first two of these are premolars, and are simpler in their form than the succeeding two teeth, which are partly divided by a median furrow into two halves. These teeth are also peculiar in that they consist entirely of vaso-dentine. They have been compared in minute structure to those of the Ray Myliobates. According to Mr. Oldfield Thomas^[17] there are seven milk teeth on each side of the upper jaw (limited to the maxillae, and thus not incisors). An eighth tooth was discovered on one side of one of the specimens examined by Thomas. In the lower jaw there are only four milk teeth on each side. It is interesting to note that the histological structure of these milk teeth agrees with that of the permanent teeth. There are two species of this genus found in Africa: the southern, O. capensis, is more hairy than the northern, O. aethiopicus. O. gaudryi is a Pliocene species from the Island of Samos and from Persia, described by Dr. Forsyth Major and Dr. Andrews.^[18] It closely resembles the existing O. aethiopicus.

Fig. 108.—Section of lower jaw with the teeth of Orycteropus. × 2. (After Owen.)

Of the Scaly Anteaters, Group Squamata or Manidae, there is really but one genus, though Phatagin, Pholidotus, Smutsia, and Pangolin have been used to distinguish various forms. The genus Manis is African and Oriental in range. Dr. Jentink, who has lately revised the species, allows seven.^[19] The external form of these animals is fairly well known, the remarkable scales distinguishing the Pangolins from other animals. Between the scales lie hairs, which seem to be absent in the adults of the African species, though present in the young, thus affording a convenient method of distinguishing the Ethiopian from the Oriental forms. The scales have been compared to agglutinated hairs. That they are not "merely mimetic of the Lizards' scales" is held by Weber,^[20] who compares them directly with those structures, as he does the scales of other mammals, such as those upon the tail of Anomalurus, etc. This, however, is not a universal opinion. It is true that these scales occur chiefly in the lower forms of mammals such as those under consideration, Marsupials, Rodents, and Insectivores; but the fact that the hairs are developed before the scales shows, or seems to show, that the former are the older structures, and to lead to the inference that the scales of mammals are new structures. The scattered hairs of the Pangolin have no sebaceous glands excepting on the snout. This, again, looks as if they were degenerate structures, and emphasises the non-archaic character of the scales. These animals have no trace of teeth except possibly some slight epithelial thickenings which have been interpreted as a last remnant; the tongue is suited for the capture of ants, and is therefore much like that of the not nearly-related American Anteaters. The stomach is of simple form; it is characterised by a large gland, which suggests that of the Koala (see p. 144); the intestine has no caecum. Retia mirabilia occur on the limb arteries. The placenta is non-deciduate and diffuse; it is specially compared by Weber with that of the Horse. Considering the many adaptive resemblances between this genus and the American Anteaters, especially in the mouth cavity, it is remarkable that in Manis the pterygoids are not joined as they are in Myrmecophaga. In spite of statements to the contrary, it appears that there is sometimes a distinct lachrymal.

A remarkable feature in the skeleton of Manis is the singular sternum. The xiphoid cartilage is extraordinarily elongated into thin strips, which reach the pelvis and return. This state of affairs is to be found in the African species only. This structure is not comparable, as it has been said to be, with abdominal ribs such as those of the reptile Hatteria.

These animals are mainly anteaters. The Japanese have a curious legend as to the method adopted for the capture of ants, which is related by Dr. Jentink in his monograph of the genus. The Manis "erects his scales and feigns to be dead; the ants creep between the erected scales, after which the anteater again closes its scales and enters the water; he now again erects the scales, the ants are set floating, and are then swallowed by the anteaters"! The same story is related by Mr. Stanley Flower on the authority of the Malays.

Though it seems clear that the likenesses which Manis shows to the Anteaters of the New World are chiefly adaptive and have nothing to do with real affinity, being merely an expression of a similar mode of life, it is curious to note that here and there we do find certain resemblances which do not seem to be susceptible of the latter explanation. The jugal bone, absent in Manis, is small in Myrmecophaga; the clavicle is absent and again small or rudimentary in the Anteaters; it is large in other Edentates. The third trochanter is absent, as in Myrmecophaga (and the Sloths). There are many scales on the body; in Myrmecophaga there are traces of these structures on the tail, as also in Tamandua. In the features mentioned, the Myrmecophagidae differ from either or from both of the two other American families (i.e. Dasypodidae, Bradypodidae) and agree with Manis. The facts are not a little remarkable.

Fig. 109.—Manis. Manis gigantea. × ¹⁄₁₂.

Order III. GANODONTA.^[21]

Allied to the Edentata, and apparently representing the ancestral forms from which they, at any rate the Xenarthra were derived, is the order of the Ganodonta. Of this order a number of genera are now known, which can be ranged in a series which more and more approaches the Edentata as we pass from the older to the newer forms. This interesting and transitional series will be made manifest by a description of the characters of the various genera taken in their proper chronological order. The following genera are included by Wortman in his family Stylinodontidae.

The earliest type of the Ganodonta is the genus Hemiganus, with but one species, H. otariidens. This animal lived during the deposition of the lowest Eocene strata, the Puerco beds of North America. It was about as big as a fair-sized Dog, and had powerful jaws. There were at least two pairs of incisors in the upper jaw, together with powerful canines and the full premolar and molar formula. In the lower jaw the canines were also strong, but the incisors are not certainly known to be more than two pairs. The enamel upon the posterior surface of the canine is thin, and in the case of the incisors the enamel seems to be limited to the anterior face. The lower molars are quadritubercular. It is believed from the presence of a suture on the upper surface of the premaxillary that the snout of the creature was tubular. The cervical vertebrae, only known by their centra, are like those of the Armadillos (and for the matter of that of the Whales) in the great transverse as opposed to the antero-posterior diameter. The feet are especially compared with those of the Ground Sloths. The single ungual phalanx is marked by a large subungual process, which is pierced by a considerable foramen. The tibia again is to be compared with that of the Armadillos.

In the Upper Puerco (Torrejon) beds the remains of Psittacotherium are found. This genus, when first discovered, was referred to the Tillodontia by some and to the Ungulates, the latter being a refuge for indeterminate Eocene mammals, just as the "Multituberculata" is for similarly-placed Secondary mammals. It is now known to be clearly a member of the order Ganodonta. Wortman thinks that there is but one species, P. multifragum. It seems to have had a general aspect much like that of Hemiganus—that is judging from the skull—and was not very greatly different in size. The facial portion of the skull is short, and the zygoma is deep. The infra-orbital canal is double, a feature which crops up in the Sloth, and has been mentioned in the later form of Ground Sloth, Megalonyx (but it must be remembered that the same characteristic is not unknown in Rodents). The dentition is reduced as compared with that of Hemiganus, that is to say, as far as concerns the molars and the incisors. There is but a single pair of incisors in each jaw; the canines are strong; the premolar and molar series seem to have been complete in the lower jaw, but reduced by one premolar at least in the upper jaw. It is very important to notice that the incisors have enamel only on their anterior faces, and that the same is the case with the canines, the slender layer present behind the tooth in Hemiganus having vanished in this later form. The tooth pattern of the molars is like that of Hemiganus. The fore-limb is decidedly Edentate-like; but it is the foot which presents the strongest likenesses to that order. "If an anatomist," remarks Dr. Wortman, "had no other part of the skeleton than that of the foot to guide his judgment, and he should fail to detect a most striking similarity between it and that of the Edentata, especially the Ground Sloths, he would not only lay himself open to the criticism of being lacking in the ordinary powers of observation and comparison, but would be suspected of placing the matter upon a basis other than that established by such a method." It is not certain how many toes upon the fore-limbs were possessed by Psittacotherium, but the close resemblance to Mylodon is indeed striking, the third digit being in both forms the most pronounced. Some vertebrae of this Ganodont have been discovered which do not show the complex articular arrangements of later American Edentates. The sacrum, on the other hand, is very like that of the Sloth, and there is a foreshadowing of the attachment of the ilia to the sacrum by co-ossification which is met with in later Edentates. A still later type is the genus Calamodon, which has been shown to occur in Europe as well as in America. C. simplex was a larger beast than either of the genera that have already been treated of, thus affording another example of the increase in size of later as compared with earlier members of the same group, so pronounced among the Ungulata. The lower jaw has the same massive structure that characterises that bone in Hemiganus and Psittacotherium. There is but one incisor, but the premolar and molar series are complete. The canine is Rodent-like in appearance, being imbedded throughout the greater part of the lower jaw; it evidently grew from a persistent pulp. It is enamelled upon the anterior face only. The premolar and molar teeth are in this genus commencing to lose their enamel, which is distributed in the form of vertical bands, leaving interspaces which are not covered by enamel. These teeth, moreover, are decidedly hypselodont, more decidedly so than in Psittacotherium; they are, when unworn, quadricuspidate, with accessory cusps; when more worn, the teeth are double-ridged, and that transversely to the long axis of the jaw; finally, the much-worn teeth have flattish crowns more or less surrounded by a ring of enamel.

A still later form, coming from the Lower and Middle Eocene strata, is the genus Stylinodon. S. cylindrifer, which is the more archaic of the two described species, is only known from a single molar, fragments of a canine, and "some inconsiderable pieces of the skull." The molar is interesting on account of the fact that the enamel is still further reduced; it is represented only by narrow vertical strips, which are much narrower than those of older forms of Ganodonts. It is also hypselodont, and has a persistent pulp. So, too, the canine which had a thick anterior facing of enamel. The later species, S. mirus, is more fully known. The teeth seem to have been much the same as in the last-described species; the premolars and molars were seven in all in the lower jaw, and the canine was imbedded in the bone for a long distance, as in Calamodon. The cervical vertebrae have short centra as in Hemiganus. The clavicles were well developed. The humerus possessed an entepicondylar foramen, and its head displays the pyriform pattern so characteristic of later Edentates. The foot is clearly like that of Psittacotherium.

In reviewing the series, therefore, we see a gradual diminution of the incisors, a gradual loss of enamel on the teeth generally, and the production of hypselodont teeth growing from persistent pulps; all of which are features of the later Edentates. The progression is so gradual that the forms enumerated and described seem to have been part of a continuous series culminating in the Ground Sloths of later times. The other points of similarity will be gathered from the facts given in the foregoing pages.

There is another family belonging to the Ganodonta whose position with regard to the Edentata is not so clear. This is the family Conoryctidae, of which two genera are known. The earliest of these, from the Lower Puerco, is Onychodectes. In O. tissonensis the skull is long and narrow, thus contrasting with that of the last family. The facial part is also long. The lower jaw is much more slender. The molar formula was complete, but there is some doubt as to the incisors. The molars are tritubercular.

The other known genus is Conoryctes. Its skull has a shorter facial portion, and is thus more like that of Stylinodontidae than that of Onychodectes. The dental formula is known, and is complete save for the loss of one incisor above and below, and one premolar above. The relationship of these Ganodonts to any later forms is uncertain; but their skeletal structure is as yet by no means fully known.

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1. Pectoral and abdominal in the Armadillo Tatusia.
2. A rather problematical Armadillo, Necrodasypus, has been recorded from French strata. It consists of a few scutes only.
3. Proc. Zool. Soc. 1882, p. 358.
4. Trans. Linn. Soc. (2) vii. 1898, p. 277.
5. i.e. large olfactory lobes.
6. Proc. Zool. Soc. 1899, p. 1014.
7. See for anatomy Owen, Trans. Zool. Soc. iv. 1862, p. 117, and Forbes, Proc. Zool. Soc. 1882, p. 287.
8. For the skull of Edentates generally see Parker, Phil. Trans. clxxvi. 1885, pt. i. p. 121.
9. The colour fades in captivity owing to the disappearance of the algae.
10. In a letter addressed to Dr. Gray, quoted by the latter in a revision of the Sloths, Proc. Zool. Soc. 1871, p. 428.
11. This name is written "Prionodos" by Gray, which might lead to a confusion with the Carnivore Prionodon.
12. For the anatomy of several forms, see Garrod, Proc. Zool. Soc. 1878, p. 222, who quotes other memoirs.
13. Flower, Proc. Zool. Soc. 1886, p. 419.
14. Milne-Edwards, Nouv. Arch. Mus. vii. 1871, p. 177.
15. See especially Lydekker, An. Mus. La Plata, Pal. Arg. iii. 1894.
16. Dr. Moreno and Mr. A. Smith Woodward in Proc. Zool. Soc. 1899, p. 144; Wiss. Ergeb. Schwed. Exped. Magellansländ. ii. 1899, p. 149.
17. Proc. Roy. Soc. xlvii. 1890, p. 246.
18. Proc. Zool. Soc. 1893, p. 239, and 1896, p. 296.
19. "Revision of the Manidae in the Leyden Museum," Notes Leyd. Mus. iv. 1882, p. 193.
20. Weber, Zool. Ergebnisse einer Reise in Niederl. Ost Indien, 1892. See also Römer, in Jen. Zeitschr. xxxi. 1896, p. 604, and Reh, ibid. xxx. 1895, p. 137.
21. See Wortman, "The Ganodonta and their Relationship to the Edentata," Bull. Am. Mus. Nat. Hist. ix. 1897, p. 59.