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Show 1903.] OF THE PERCY SLADEN EXPEDITION. 239 Type. Adult male. B.M. No. 3.7.7.71. Original number 1050. Collected 30 July, 1902. The difference in the structure of the pterygoid fossa?, perfectly uniform throughout the series, seems to make it necessary to give a special name to the Matto Grosso Water-rat; but as lower down the same river, in Paraguay, specimens agreeing with the true N. squamipes occur, I only distinguish it as a subspecies. It may be noted as a curiosity that a very large proportion of the skulls of Nectomys, even when quite old, have their median interparietal suture open, a characteristic very rare in mammals generally. 20. ORYZOMYS LATICEPS Lund. 6. 1003, 1007, 1008, 1020, 1052, 1053, 1062. 2 . 1004, 1006, 1010, 1016, 1026, 1049. These specimens appear to be certainly identical with those obtained by Mr. Robert on the Rio Jordao *, S. Minas Geraes, not far from the typical locality of the species. 21. NEACOMYS SPINOSUS AMCENUS, subsp. n. tf. 1061, 1077, 1188. §. 1036, 1051. Size averaging slightly larger than in the true Peruvian N. spinosus, and tail rather longer. General characters very much as in that animal, in spite of the great distance between the localities. Fur shorter and thinner than in spinosus, especially on the under surface. Colour above bright ochraceous, liberally lined with black along the back, but the dorsal area nevertheless not nearly so dark as in spinosus. Sides clearer fulvous, the yellowish line along their lower edge not so sharply defined as in spinosus. Belly and inner sides of limbs white, the hairs white to their roots ; line of demarcation not very sharply defined. Face rather greyer than body. Ears uniformly brown. Arms and legs like sides, or rather duller; hands and feet dull whitish. Skull as usual varying a good deal in size and shape, but in a general way that of subsp. amcemis is a little larger than that of spinosus, with more rounded brain-case, less developed supraorbital ridges, and slightly larger palatal foramina, but none of these points can be regarded as really distinctive. Dimensions of the type, measured in the flesh :- Head and body 90 m m . (extremes 80-90); tail 102 (102-112); hincl foot (s. u.) 23 (22-24), (c. u.) 24-5 ; ear 16 (14-16). Skull-greatest length 24-6mm.; basilar length 18'1; zygomatic breadth 12-7; interorbital breadth 4'3 ; palatal foramina 4; length of upper molar series 3*1. Type. Old male. B.M. No. 3.7.7.84. Original number 1077. Collected 11 August, 1902. The occurrence of a Neacomys in this region was quite * Of. Ann. Mag. N. II. (7) viii. p. 530 (1901). |
