OCR Text |
Show MAMMALIA. .)9 colour of the ordinary fur, a dark brown tint; chin, throat, chest, and rump, white; the hairs covering the upper surface of the feet are of a dirty yellowish-white colour, and on the toes nearly white : ea1·s densely clothed with longish hairs, those on the inner side chiefly of a deep golden colour, and those on the outer side brownish; the ears are partially hidden by the long fur of the head ; tail sparingly clothed with hairs, above brown, and beneath brownish-white : the fur of the back is of a deep gray colour at the base, annulated with deep golden yellow near the apex, and blackish at the apex ; the longer hairs are black; the hairs of the belly are pale gray at the base, and broadly tipped with golden yellow colour; the white hairs on the throat, chest, and rump are of an uniform colour-not tinted with gray at the root ;- the hairs of the moustaches are black : the incisors of the upper jaw are of a deep orange colour, and those of the lower jaw are yellow: the thumb nail is truncated. Length from nose to root of t~il of tail from nose to e~r In. Lines. 8 7 Habitat, Bahia Blanca, (Sep tember.) Length of t~rsus of c~r In. Lines. This species is nearly equal in size to the common rat (.Llfus decumanus). Of its skull* I possess but the anterior portion (see Pl. 33. fig. 3, a. and 3, b.): it appears to have been about the same size as that of M. decumrmus, its proportions, however, are different: the nasal portion is broader and shorter, the ant-orbital outlet is rather smaller; the plate, forming the anterior root of the zygomatic arch, and which protects this outlet, has its anterior edge distinctly emarginated, and not nearly straight as in M. decumanus, - thc zygomatic arch is stouter, the space between the orbits is narrower, the palate is more contracted, the incisors are much broader, less deep from front to back, and have the antel'io1· surface more convex; the molar teeth are larger; the lower jaw (see Plate 34. fig. 12, a.) when compared with that of .Dfus decumanus also offers many points of dissimilarity ; the principal differences consist in its greater strength, the comparatively large size and breadth of the articular surface of the condyles, the upt·ight position of the coronoid process- a perpendicular line dropt from the apex of which would touch the posterior part of the last molar-and the great • I ~m sorry to say the artist has not dmwn this skull with his usual fidelity, a circumstance which I did not perceive until it was too !~to to make any ~Iteration: it is too largo, and tho incisors arc represented as projecting forw~rds too much ; they ~ro in tho origiu~l 80 no~rly at right ~nglcs with the upper surface of the skull th~t but ~ very sm~ll portion of them is seen, when it is viewed, as represented at fig. 3, lt. |