The valuable natural history material brought by the Arctic explorer, Commander R. E. Peary, U. S. N., to the American Museum of Natural History on his return from his recent long sojourn in the high North contains five specimens of Caribou taken in Ellesmere Land, Lat. 79°, in June, 1902. They comprise four flat skins of adults without skulls, and more or less defective, and the complete skin of a young fawn. In colouration they are strikingly different from any other known Caribou, being pure white except for a large dark patch on the middle and posterior part of the back. ELLESMERE LAND CARIBOU _Rangifer Pearyi_, sp. nov. Type, No. 19231 ♂ ad., Ellesmere Land, N. Lat. 79°, June 15, 1902, Commander Robert E. Peary, U. S. N. Entire animal pure white except an oval grayish brown patch over the posterior half of the dorsal surface, gradually fading into white toward the shoulders, the hair being white to the base, or of a pale shade of lilac below the surface, where the surface colour is white. The dorsal patch occupies an area of about 670 mm. in length by 350 mm. in width, and is drab-gray, divided by a very narrow median line of white. The legs and feet are wholly white; the ears are slightly tinged with gray, the hair beneath the surface being plumbeous and showing slightly at the surface. The antlers are just budding, being represented by small protuberances, about an inch and a half in length, covered with short hair. Total length of flat skin, 1660 mm. Corresponding measurement of flat skins of the dark form of Caribou from Greenland, 1820 mm. A female (No. 19232) is similar, except that the dark dorsal area extends a little further forward at the shoulders, and is a little darker. As in the male, the patch fades out to whitish toward the shoulders. Length of the flat skin, 1560 mm. Two other females are similarly marked, but the dorsal patch in both is much darker, approaching dark slate gray. The region around the base of the antlers and ears is clouded with grayish, as are the edges of the ears; the front surface of the forelegs is dark grayish brown, and of the hind legs faint buffy grayish brown, increasing in amount and intensity apically from the tarsal joint to the hoofs. These skins measure respectively 1610 and 1570 mm. in total length. In one the antlers form knobs an inch or two in height, covered with short hair.