Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/437

Rh KODENTIA.] MAMMALIA 415 FIG. 88. Head of CentuHo senex. Dobson, Cat. C/iiropt. Brit. Mus. in / (rarely equal to) the distance from the eye to the extremity of the muzzle ; uosc-leaf short, horse-shoe-shaped in front, lanceolate behind (except in Brachyphylla and Ccnturio); in terfemoral mem brane always concave behind ; tail none ; inner margin of the lips fringed with conical papilla; ; i f or -?-, pm f, m f or f or f ; premolars and molars very broad (except in Sturnira), the latter with concave or flat crowns margined externally by raised cutting edges. Although the Stenoderiiiata are generally easily distinguished from the Vampyri by the peculiar shortness and breadth of the muzzle, and by the form of the molar teeth, certain species of the latter group closely resemble those of the former in external appearance, agreeing almost absolutely in the form of the nose-leaf, of the ears and tragus, and of the warts on the chin. These resemblances show that, while the form of the teeth and jaws has become modified to suit the food of the animals, the external characters, being but slightly affected by this cause, have remained much the same, and now indicate their common origin. The food of these Bats appears to be wholly or in great part tree fruit. The twenty species have been divided into nine genera, distinguished by the form of the skull and teeth. Artibcus, with five, includes among them the well-known frugivorous Cat, A. perspicillatus of Linnaeus, so common in collections. Stenodcrma achradophilum, found in Jamaica and Cuba, associated with the above, and scarcely distinguishable externally except by its very much smaller size, differs altogether in the absence of the horizontal plate of the palate bones. Sturnira lilium, while agreeing with the above in the form of the nose -leaf and ears, differs from all the species of the family in its longitudinally-grooved mo lars, which resemble those of the frugivorous Pteropodidse more closely than those of any other Bats ; and the presence of tufts of long differ ently-coloured hairs over glands in the sides of the neck shows 3 et another character in common still more remarkable, which can scarcely be considered, like the teeth, the result of adaptive change. Ccnturio senex is the type of a genus distinguished from Stenodcrma and other genera of this group by the absence of a dis tinct nose-leaf. This most remarkable form stands alone among the species of Chiroptera, and, indeed, in its peculiar and grotesque physiognomy is unrivalled among known mammals. Group IV. Dcsmodontes. Muzzle short and conical; nose-leaf distinct ; in terfemoral membrane very short ; tail none ; i, pm f, m { or $ ; upper incisors very large, trenchant, occupying the whole space between the canines ; premolars very narrow, with sharp- edged longitudinal crowns ; molars rudimentary or none ; stomach greatly elongated, intestiniform. There are two genera, Dcsmodus, without calcancum or true molars, and Di-phylla, with a short calcaneum and with a single rudimen tary molar on each side, restricted to Central and South America. Dcsmodus rufus, the commoner species, is a little larger than the Noctule Bat of Europe, and abundant in certain parts of South America, where it is very troublesome owing to its attacks upon domestic animals, sucking their blood and often leaving them much weakened from repeated bleedings. See VAMPIRE. FOSSIL CHIROPTERA. Fossil remains of Chiroptera extend as far back as the Upper Eocene of Europe and America, if, indeed, the beds in which they have been found are rightly considered as belonging to that age. Of these Vcspcruyo (Nyctitherium) parisiensis, described by Cuvier from the gypsum of Montmartre, is very like a small specimen of the widely distributed V. serotinus ; V. velox and priscus of the same subsection, and Nyctilc&tes serotinus, have been characterized by Marsh from the Eocene of the United States, and Vespertilio morloti, Pictet, from that of Switzerland. From the Quercy lacustrine deposits comes EMnoloplius antiquus, Filhol, but these are very doubtfully of Eocene age. Paleeonycteris (allied to RMnolophus), with P. robustus, Vespcrugo, with V. noctuloides and murinoides, and Vespertilio, with V. aquensis, pr&cox, and insignis, have been found in Miocene beds of France and Germany. Pliocene bone caves have also yielded remains, in all cases closely allied to species now inhabiting the same countries. All these forms, however, exhibit as much specialization in their general structure as any existing species of the same families, indicating (if the age assigned to the deposits can be trusted) that the first appearance of Ghiroptcra must be referred to a very remote period. Bibliography of Chiroptera. G. E. Dobson. Catalogue of the Chiroptera in the Collection of the British Museum, 1878, including descriptions of all the species of Bats then known; subsequent papers by the same author in Rep. Brit. Assoc. Adv. Science, f roc. Zool. Soe., Ann. May. Nat. Hist., and Bullet. Soc. Zool. do France, by Peters in MonaUb. Akad. Wissensch. Berlin, and by Oldfield Thomas and J. Scully in Ann. Mag. Nat. Hist. ; H. A. Robin, Recherches Anatomiqiies sur lei Mammifcres d? VOrdre dts fhiropteres, Paris, 1881. OHDEK KODENTIA. Terrestrial, rarely arboreal or natatorial, dipliyodont placeutal mammals of small size ; with plantigrade or semiplantigrade, generally pentadactyle, unguiculate, rarely subungulate, feet ; with, clavicles (sometimes imperfect or rudimentary) ; with never more than two incisors in the mandible, and without canines. The upper incisors resemble the lower in growing uninterruptedly from persistent pulps, and (except in Lagomorplia) agree with them in number ; the premolars and molars are rooted or rootless, with tuberculated or laminated crowns, and arranged in an unbroken series ; the orbits are not circumscribed by bone; the mandibular con- dyle is antero-posteriorly elongated ; the intestine (except in MyoxidaR) has a large caecum ; the testes are inguinal or abdominal; the uterus is tw.o-horned, the cornua opening separately into the vagina or uniting to form a corpus uteri; the placenta is discoidal-and deciduate; and the smooth cerebral hemispheres do not extend backwards so as to cover any part of the cerebellum. The Rodents form a very compact order, jeadily distinguished by their large chisel-shaped incisors, and by the absence of canines. They include by far the greatest number of species (owr 900), and have the widest distribu tion, of any of the orders of terrestrial mammals, being in fact cosmopolitan, although more abundant in some parts, as in South America, which may be considered their head quarters, than in others, as in Australasia and Madagascar, where representatives of a few genera of one family (Mttridse) only are found, thus contrasting remarkably with the Insectivora, which constitute at least half the mamma lian fauna of Madagascar, but are without living represen tatives in South America. If, as we have seen, the term entomophagous is applicable to most Insectivora, much more so, on the other hand, may the species of this great order be defined as phytophagous, and this uniformity in their food and in the mode of obtaining it, namely, by gnawing, has evidently led to such corresponding general uniformity in structure, which is observable throughout the species, that with difficulty we obtain characters sufficiently salient for divid ing them into genera and families. Although, like the Insectivora, they present much diversity of habit, some being arboreal, as the Squirrels, many species of which are provided with cutaneous parachutes on which they glide from tree to tree ; some cursorial, as the Hares ; some agile jumpers, as the Jerboas; some fossorial, as the great Mole- Rats ; and some natatorial, as the Beavers and Water-Rats, yet we do not find corresponding structural modifications comparable with those noticed in that order. OSIY- AS Per FIG. 89. Side View of Skull of Cape Jumping Hare (Pedetes coffer), x f. PMx, prcmaxillu ; MX, maxilla ; Ma. malar ; Fr, frontal ; L, lachrymal ; Pa, parietal ; Na, nasal ; Sq, squamosal ; Ty, tympanic; rO, exoccipitat ; AS, alisphcnoid ; OS, orbito-sphenoid ; Per, mastoid bulla. Flower, Osteal. Mammal. The Rodent skull is characterized by the great size of the premaxillary bones, which completely separate the nasals