Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/405

Rh EDENTATA.] pressed and tapering, bevelled at the ends. Premolars and molars in continuous series, as in the upper jaw. Fore feet with the two inner toes slightly separated from and opposable to the re maining three, all with strong, curved, and much compressed claws. Hind foot with the hallux placed very far back, large and broad, the second and third (united) toes considerably smaller than the other two ; the fourth the largest. No external tail. Fur dense and woolly. Ears of moderate size, thickly clothed with long hairs. Vertebra : C 7, D 11, L 8, S 2, C 8. Ribs eleven pairs, a rare ex ception to the usual number (13) in the Marsupialia. There is but one species, the Koala or Native Bear of the Australian colonists (P. cincreus], found in the south-eastern parts of the Australian continent. It is about 2 feet in length, and of an ash-grey colour, an excellent climber, and residing generally in lofty Eucalyptus trees, on the buds and tender shoots of which it feeds, though occasionally descending to the ground in the night. Kindred Fossil Forms. Here may be noticed several genera of extinct Marsupials, the remains of which have been found in the post-Tertiary deposits of Australia, which agree with the Macropodidie and the Phalangistidae, in having f incisors, those of the lower jaw very large and proclivous. As the whole of their structure, especially that of the hind feet, is not yet known, their precise affinities cannot be determined. Diprotodon. Dentition: if-, c -, p -J-, m f ; total 28. The first upper incisor very large and scalpriform. True molars with pro minent transverse ridges, as in Macrojms, but wanting the longi tudinal connecting ridge. Anterior and posterior limbs less dis proportionate than in the- Kangaroos. t&amp;gt;. australis is a gigantic animal compared with all existing Marsupials, surpassing a Rhino ceros in bulk. Nototheriuin. Dental formula as in the last, from which it differs chiefly in the incisor teeth, especially those of the lower jaw, being much smaller. The skull is short, with the zygomatic arches extremely broad. N. mitchelli and inerme, both animals of great size, though inferior to Diprotodon. Thylacoleo. Dentition of adult: i f-, c ^, p f, in |; total 24. First upper incisor much larger than the others; canine and first two premolars rudimentary. In the lower jaw there are also one or two small and early deciduous premolars ; posterior premolars of both jaws formed on the same type as that of Bypsiprymnus, but relatively much larger; true molars rudimentary, tubercular. One species, T. carnifex. This animal presents a most anomalous con dition of dentition, the functional teeth being reduced to one pair FIG, 33. Front View of Skull of Thylacoleo carnifex, restored. X. From Proc. Gtol. Soc., 1868, p. 312. of large cutting incisors situated close to the median line, and one great, trenchant, compressed premolar, on each side above and below. It was first described as a carnivorous Marsupial, and named, in accordance with its presumed habits, &quot;as one of the fellest and most destructive of predatory beasts ;&quot; but, as its affinities are certainly with the Phalangistidae. and Macropodidse, and its den tition completely unlike that of any known predaceous animal, this view has been called in question. 1 1 The lowest Eocene formation of New Mexico has recently yielded an animal (Ptilodus mediasvus) having a mandibular dentition allied to that of Thylacoleo, and which goes some way to bridge over the gap, both in structure and time, between this and the Mesozoic Plagiau- lacidx (see Cope in American Naturalist, June 1882). 383 Family PHASCOLOMYID.K. Dentition : c |, i {j, p, m } = 24. All the teeth with per sistent pulps. The incisors large, scalpriform, with enamel only on the front surface, ns in the Rodcntia. The molars strongly curved, forming from the base to the summit about a quarter of a circle, the concavity being directed outwards in the upper and in wards in the lower teeth. The first of the series (generally called &quot; premolar,&quot; though it appears to have no milk predecessor) single- lobed ; the other four composed of two lobes, each subtriangular in section. Limbs equal, stout, and short. Fore feet with five distinct toes, each furnished with a long, strong, and slightly curved nail, the first and fifth considerably shorter than the other three. Hind feet with a very short nailless hallux, the second, third, and fourth toes partially united by integuments, of nearly equal length, the fifth distinct and rather shorter ; all four provided with lung and curved nails. In the skeleton of the foot, the second and third toes are distinctly more slender than the fourth, showing a slight tendency towards the peculiar character so marked in the last three families. Tail rudimentary. Stomach simple, provided with a special gland situated near the cardiac orifice. Cfecurn very short, wide, and with a peculiar vermiform appendage. The species of this family are few, and all contained in one genus, Phascolomys, with two well-marked sections, one containing the Common and Broad-nosed Wombats, P. wombat andplatyrhinus, the other the Hairy-nosed Wombat, P. latifrons. They are all terres trial and burrowing animals, generally slow in their movements, and harmless in disposition ; they feed on roots and other vegetable substances, and inhabit the southern parts of the Australian con tinent, Tasmania, and the islands of Bass s Straits. See WOMBAT. Bibliography of Marsupialia. G. R. Waterhouse, Nat. Hist, of the Mammalia, vol. i. &quot;Marsupiata,&quot; 1846; J. Gould, Mammals of Australia, 1863; K. Owen, article &quot; Marsupialia,&quot; in Cyclop, of Anatomy and Physiology, and various memoirs &quot;On Extinct Mammals of Australia&quot; in Philosophical Transactions; W. II. Flower, &quot; On the Development and Succession of the Teeth in the Marsupialia,&quot; Phil. Trans., 1867. SUBCLASS EUTIIEKIA OR MONODELPHIA. The remaining mammals are included in the EUTHERLA, PLACENTALIA, or MONODELPHIA, the leading characters of which have been given at p. 372. Their affinities with one another are so complex that it is impossible to arrange them satisfactorily in any serial order. The Edentata may be taken first as standing in some respects apart from all the others. The Sirenia and Cetacea are also somewhat isolated, having undergone most remarkable modifications from the normal mammalian type. The Primates must be placed at the head of the series. The position of the others is quite arbitrary, as none of the hitherto proposed associations of the orders into larger groups stand the test of critical investigation, and palseontological researches have already gone far to show that they are all modifications of a common heterodont, diphyodont, pentadactyle form. ORDER EDENTATA. The name assigned to this group (which some zoologists think ought rather to be ranked as a subclass than an order) by Cuvier is often objected to as inappropriate, for though some of the members are edentulous, others have very numerous teeth ; and the Linnsean name Brut a is occasionally substituted. But that term is quite as objec tionable, especially as the group to which Linnaeus applied it is by no means equivalent to the order as now under stood, as the names of the genera contained in it, viz., Elephas, Trichechus, firadypus, Myrmecophaya, Manis, and Dasypus, will indicate. It contained, in fact, all the animals then known which are comprised in the modern orders of Proboscidea, Sirenia, and Edentata, together with the Walrus, one of the Carnivora. If retained at all, it should rather belong to the Proboscidea, as Elephas stands first in the list of genera, and was probably in the mind of Linnaeus when he assigned the name to the group. Cuvier s order included the Ornithorhynclms and Echidna, the structure of which was then imperfectly known, and which are now by common consent removed to an altogether different section of the class, but otherwise its limits are those now adopted. The name Edentata is so generally used, and its meaning so well understood, that it would be very undesirable to change it now ; in fact similar