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Show 4'2 ZOOLOGY OF THE VOYAGE OF TilE DEAGLE. ln. Lines. 0 10 Length from nose to root of tail of tail In. Lines. 3 7 3 Length of tarsus of car 0 from nose to car Habitat, Bahia Blanca, (Septernber.) Upon comparing the skull (Pl. 34, fig. 2, a.) of ~f. elegans with that of 1lL Musculus, the most evident points of distinction consist in the greater proportionate length of the nasal and frontal bones, and the slenderness of the zygomatic arch in the former animal. Length of skull 11 lines, width 6 lines, distance between front molar and outer side of incisors of upper jaw 3~ lines, length of nasal bones 4i lines. The dentition is figured in Pl. 34, figs. 2. b, and 2. c. "Whilst bivouacking one night on shore, amongst some sand hillocks, this mouse, with its tail singed, leapt out of a bush which was placed on the fire. Its hind legs appeared long in proportion to the front, and it did not appear to be very active in endeavouring to make its escape."-D. Mns elegans is about equal in size to M. ~luswlus; the head is larger in proportion than in the latter, the cars are slightly larger, the tail is longer, and so are the tarsi. The large ears, long tail, and comparatively large size of the feet, combined with the greater size of the animal itself, will render it easy to distinguish this species from III. gracilipes and ~!f. binwculatus. From the last mentioned animal it moreover differs in having the head larger in proportion , the fur longer, and the colouring of the upper parts of the body somewhat darker. The white fur is almost confined to the under pmts of the body, and there is but a small tuft of white hairs behind the ears, whereas in lJ!. bimaculatus, the white fur extends considerably on tho sides of the body, the outer side of the limbs arc white, and there is a large and conspicuous white spot behind each car. In lJ!l. elegans the whole sole of the tarsus and the carpal tubercles arc covered with hair. In Mus bimaculatus the hinder ltalf of the tarsus only is covered with hair, and in M. gracilipes both the hinder half is covcreu, and there are some scattered hairs extending almost to the two tubercles, which arc situated at the base of the longer toes. The genus Eligrnodontia of M. F. Cuvier, founded upon a species of mouse from Buenos Ayres, possesses nearly the same characters as the subgenus Calomys, established by me in the Proceedings of the Zoological Society for February 1837, and which included the animal above described, and two other · species (M. bimaculatus and JJI. gracilipes). M. Cuvicr's genus is distinguished by there being only one large tubercle on the under side of the tarsus, and in having the carpal pad covered with hair as well as the pad of the tarsus. In liiAl\Il\f ALIA. these characters our present .... n· 1 4 . .. una agrees as 't d 1 · . :l proportwns of the tail and tarsus c·. ' l oes a so m Size and in the relative are identical. ' ncumstances which induce me to believe ~hey In M. bimaculattts and JilT . .·z· d · ~. g1acz zpes there ar · un or stde of tho tarsus and theca I .1. e SIX naked tubercles on the l · ' ' rpa pau IS also n k d 1 . tarsus tauy beneath,* in dentition "I1'1 . l . a e . n havlllg, however the M l " u In co ounng th ' . e egaus that I think they cannot b ' ey agree so closely with e separated genericaHy. Mus BIMACULATus. PLATE XII. l\Ius bimaculatus, Tl'atede., Proceedings of the ZooloO'ical S i t f L "' oe e yo ondon for February 1837, p. 18. JJI. vel!e re pallide ocltr aceo, pz· zt·s nz·o -n·c antibus ad . h . Lateribus, no ttl ma o·na po1te a ~ . spm so, tts ad latera mrioribus; rostri • 7 • 0 urem utramque artubus aunvus medioc1·ilnts . cauda n l l . . ' ' corporeque subtus niveis . l . . ' ' :1. uoac. ongzlttdmem cor j' ' ca cem pzhs argeuteo-candidis obsitis. ' pus ere tequanle; tarsis ad DESCRI1'TION.-Uppcr parts of th b d f hairs, however are bla k ~1 o yho a very pale ochre colour, the lono-er , ~ ~ c , anu at t e apex . .· h d . . o numerous, as on the b ... k d . gia}IS , an where they are .. c an upper sudac f tl h d depth to the colourinn-. the cheek d ': I c o Je ea ' they give greatei· uniform palo, but bri~l;t clio . s an. su cs of the body are of an almost the chocks, the lowct· ~ort!on a;:~ otf~:h~~~~s off the muzzle, the lower half of under parts are pure . I 't . es .o the body, and the whole of the and not as i's usuall tlw u e-each Iuur bemg uniform in colour to the root ' Y 1c case o.,.ay at the . t Th . . . ' patch of pure white hairs b I ~ .sd •I lOO • ere IS ltkewJse a large flesh-colour, and furnished ,:i~;:1 . ~~~ llea~·· Tl~e f~et and tail are of a pale the upper surface of the I tt .w JI ~I laus, wtth the exception of those on 1 a ei, w uc 1 arc pale b 'l'h pa e flesh-colour, clothed internall . . rown. e ears are also part, the hairs arc brownish d y ~Ith ~ellow hmrs; externally on the fore large, and so are the feet ';~ ~n·~ l~ lnnder part, white- they are rather The hairs of th . 1e at IS about equal to the body in length. arc black at the\ ~oustaches are numerous and slender, and most of them ase, and gray at the apex. The hinder half of the tarsus ." ln Afus leucopus of North America tho . . . anunal also <lgrccs wi tl tl . tarsus Is hauy beneath, and Ill tho character of the teeth tldij 1 10 spcciCs above mentioned. |