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Show 40 ZOOLOGY OF TIIE VOYAGE OF THE DEAGLE. The most conspicuous characters of the present species consist in the immense length of the tail, and the great size of the hinder feet.* It is about e11ual in size to JJfus Musculus; its form, however, is somewhat stouter; in colour it is much paler and brighter. 'l'he head is lm·ger in proportion ; the ears are smaller, and more densely clothed with hair; the fore feet are rather larger, and the fleshy tubercle on the under side of the wrist is also large!'. The thumb nail is flattened, and rounded at the tip, as in Mus Mttsculus, but is longer, and more distinct than in that animal. The skull of JJf. longicaudatus, (Plate 34, Fig. 1 ,) is considerably lal'ger than that of the common mouse, but in form scarcely differs from it; its upper surface is rather more coovex, and the interparietal bone proportionately less. The length of the skull is 1 inch; breadth, G~ lines; distance between the fore part of the incisor, and the first molar of the upper jaw, 3t lines. The dentition is figured in Plate 34, Figs. 1. b and 1. c. The above account is drawn up from the same specimen as that from which Mr. Bennett took his description, and which was brought from Chile by Mr. Curning, who states that the animal in question lives in trees, and constructs its nest with grass. In Mr. Darwin's collection, I find an animal which agrees in all the more im-portant charaeters with the one above described, but differs in being of a deeper colour, (approaching more nearly, in this respect, to the common mouse,) and in having the tail a trifle shorter. The skull is about i of a line shorter, but its proportions agree precisely : the proportions of the feet, and the general form of the animal, also agree. This specimen is likewise from Chile, (Lat 37° 1!0',) and, according to Mr. Darwin, "overran the wooded country south of Concepcion, in swarms of infinite numbers. Captain FitzRoy, on his return from visiting the wreck of H. M. S. Challenger, had the kindness to bring me this specimen. So destructive was this little animal, that it even gnawed through the paper of the cartridges belonging to the people who were wrecked."-D. * A long tarsus is generally accompanied by a proportionately long tail. I presume that those Mice which have long tarsi are in the habit of making great leaps, and that in these leaps, the tail serves to steady and balance the body. |