Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/15

Rh M O U M O U Columbus. Settled in 1805, it had become a well-built flourishing place of 5249 inhabitants in 1880, engaged in various manufacturing industries. MOURZUK, or MURZUK. See FEZZAN, vol. ix. p. 130. MOUSE. The bright and active, though mischievous, little animal known to us by the name of Mouse and its close relative the Common Rat are the most familiar and also the most typical members of the Murinx, a sub family containing about 250 species assignable to no less than 1 8 distinct genera, all of which, however, are so super ficially alike that one or other of the English names rat or mouse would be fairly appropriate to any of them. Together they form one, and that by far the largest and most important, of the 10 sub -families into which the Muridae or Rat family (order Rodentia) are divisible. Their nearest neighbours are the Tree-mice (Dendromyinse) and the Hamsters (Cricetinee), from which they differ by various cranial and dental characters. Among themselves they have for the most part very strong resemblances ; nearly all are of very rat-like exterior, of light and active build, with large ears, bright and well-developed eyes, long and Fig. 1.- -The Australian Brown-footed Rat (Mus ftiscipes, Waterh.) (After Gould.) scaly tails, and nearly always of dull and inconspicuous coloration, as is suitable to their usually burrowing and nocturnal habits. The more important characteristics of the group, their anatomical, cranial, and dental peculiarities, have already been touched upon in the article MAMMALIA (vol. xv. p. 415 sq.), and therefore we may now pass to the division of the sub-family into smaller groups. Primarily the Murinse are divisible into the Mures, or those with their molar teeth, as in the Common Rat, and the Sigmodontes, or those with their molars, like those of the Rice -rat of America. Fig. 2 will explain this : A represents the upper molars of a Mus, and B the correspond ing teeth of a Sigmodont. It will thus be seen that Mus has molars composed essentially of cusps arranged triserially that is to say, with three series of cusps across each tooth while in the Sigmodontes the cusps are arranged bi- serially in pairs along the teeth. To the first of these groups, the Mures, be long the following genera : I. Mus, L. Incisors narrow, not grooved. Molars small, their us. B. Upper mo lars of Sigmodont. structure as shown in fig. 2, A. Incisive foramina long. Coronoid process of lower jaw well developed. Eyes and ears large. Fur soft, though sometimes mixed with spines ; pollex with a short nail instead of a claw. No cheek-pouches. Tail long, nearly naked, with rings of overlapping scales. This, the typical genus of the family, is by far the largest of the order, and indeed of the whole class Mammalia, containing not less than 120 species spread over the whole of the O n d World with the exception of Madagascar. Of these, about 30 belong to what is known as the Paltearctic zoological region, 40 to the Oriental, 30 to the Ethiopian, and 20 to the Australian, the number of species being on the whole much more considerable in tropical than in temperate regions, while but very few are found where the climate is excessively cold. It is an interesting fact in connexion with climate that many of the species living in hot countries have their fur more or less mixed with flattened spines, and that these spines appear to be shed during the winter and to be replaced by hairs, the latter naturally affording a warmer covering for the animal than the former. The most important characters that have been used for the deter mination of the various species of Mus are the size and proportions of the body, limbs, ears, and tail, the number of mammte, which ranges from 6 to 20, and various more or less important differences in the shape and proportions of the skull and teeth. Of the numer ous species the following are those most worthy of note : Mus decumanus, Pall., the Common Brown or Norway Rat, dis tinguished by its large size, brownish grey colour, short tail and ears, powerful skull, and the possession of from 10 to 12 mammse. It is extremely fierce and cunning, and easily overcomes in the struggle for existence all the other allied species with which it comes in contact. Its original home would seem to have been some part of Central Asia, an indigenous species recently described from China, M. humiliates, being in fact so extremely like it that in all probability the latter is the original race from which it has sprung. Thence it has spread to all parts of the world, driving out the house-haunting species everywhere, as it has in England all but exterminated the next species. M. rattus, L., the old English Black Rat, readily distinguishable from the Brown Rat by its smaller size, longer ears and tail, and glossy black colour. It shares the roving habits of M. decumanus, frequenting ships, and from them passing to the land in various parts of the world. On this account it, or its tropical representa tive M. alcxandrinus, Geof., is extremely common in many places to which M. decumanus has not yet penetrated, for instance in South America, where it has had only the far less highly-organized Sigmodontes to compete with, and where it has therefore gained a firm footing. It is extremely interesting to observe that this long- tailed rat, originally a native of India, would seem to have first penetrated to all parts of the world and to have overcome and nearly or quite exterminated the indigenous rats, and that then M. decumanus, a more recent and powerful development of the House-rat type, has followed, and in its turn has overcome and nearly exterminated it. M. musculus, Linn., the Common House-mouse, is, like the last species, originally a native of India, whence it has spread to all the inhabited parts of the globe. Its habits and appearance are too well known to need any description. M. sylvaticus, L.,the Wood or Long-tailed Field-mouse. is a species very common in many parts of England, often taking to barns and outhouses for shelter during the winter. It is of about the same size and proportions as M. musculus, but of a bright reddish grey colour, with a pure white belly. M. minutus, Pall., the Harvest -mouse, is the smallest of the European mice, seldom exceeding 2 or 3 inches in length. It i.s of a yellowish red colour, with comparatively short ears and tail. It lives entirely away from houses, commonly taking up its abode in wheat or hay fields, where it builds a round grass nest about the size of a cricket-ball, in which it brings up its young. These five English species may be taken as types of the 120 species of Mus. None are much larger than M. decumanus or smaller than M. minutus, and they all have habits generally similar to those of one or other of the English species, although there are some which either live in trees like squirrels, or in the water like the English Water-voles, among which latter is the species shown in fig. 1, M. fuscipes, Waterh., the Brown-footed Rat of western and southern Australia. II. Nesokia, like Mus, but with the incisors and molars very much broader, and the transverse lamina; of the latter more clearly defined. This genus, so closely allied to Mus as to be barely worthy of separation, contains five or six species of clumsily-built rats spread over southern Asia from Palestine to Formosa, and from Cashmere to Ceylon. The most noteworthy member of the group is the Great Bandicoot or Pig-rat of the continent of India (^V. bandicota, Bechs. ), the largest of all the rat tribe, often considerably exceed ing a foot in length. The other species vary in size between this and a brown rat. W. bengalcnsis, Gr., the common Field-rat of