322 Mr. Oldfield Thomas on a neio Species of which are narrow, especially the latter, and defined by dis-tinct margins. Colour light brown, covered with a very thin epidermis. Interior whitish, inclining to a pinkish tint to-wards the umbones ; and the extreme outer edge is pinkish red and smooth. Hinge composed of a single tooth in the right valve, and two diverging ones in the left. Lateral teeth in right valve consisting of a thin marginal raised acute ridge extending nearly as far as the anterior dorsal slope. A similar ridge is met with in the left valve, only on the posterior dorsal margin. In each valve on the opposite side to the ridge is a narrow groove for the reception of the ridge in the oppo-sing valve. Muscular scars small, posterior one the narrower. Diam. 15 millims., length 12i, thickness 6. Hah. 52° 45' S. lat, 50° 39' W. long., 48 fms. East of Uruguay. This species is remarkable on account of the squareness of its form, especially at the anterior extremity. XL. — Description of a new Species of AxviccAa, from Northern India. By Oldfield Thomas, E.Z.S., British Museum. Among the collections received by the British Museum from the India Museum at South Kensington was a specimen labelled and entered in the catalogue as Cricetus songarus (Pall.) *. When the skull was extracted, however, it proved to be, not a Cricetus, but an Arvicola, quite distinct from any species yet described. It was collected in Kumaon by Capt. (now Lieut.-Gen.) R. Strachey, after whom I propose to name the species Arvicola Stracheyi, sp. n. General colour of the fur above pale brownish grey, the hairs being of a slaty blue colour for three fourths of their length and their ends being brownish yellow tipped with black. On the belly the light tips are replaced by pure white. Ears rather short, scarcely showing beyond the fur, and thickly clothed with hair coloured like that on the back. Feet and tail pure white, the latter with a terminal pencil of hairs nearly half an inch long. Thumbs quite rudimentary. The dentition of this species is very interesting, as the third upper molar is of a most remarkable type, and one apparently peculiar to the Arvicolas of this region, the only other species at all resembling A. Stracheyi in this respect being A. Sto-liczlcana, Blanf.f, from Yarkand and Ladak; but even in that the peculiarity is not so strongly marked. * Horsfield, Cat. Mamni. Mus. E.I. Comp. p. 145 (18-51). t W. Blanl'ord, J. A. S. B. 1875, pt. ii. p. 147 ; Mamm. Yark. Exped. p. 43, pi. viii. %. 1 (animal), pi. x. B. fig. 2 (skull and teeth).
BioStor
