In one instance the song had been heard in a china closet and an observer sat by the open door to locate the singer. After patient waiting “a mouse peered out from behind the plates, climbed up a little way on the brackets, and after looking around several times, began to sing.” This mouse continued to sing in the same place at intervals for several weeks and became accustomed to the presence of people during its performances; then it suddenly disappeared, probably a victim to one of the dangers which constantly beset its kind. =THE MOUNTAIN-BEAVER= (=Aplodontia rufa phaea= and its relatives) (_For illustration, see page 534_) The first adventurous fur traders who penetrated the Oregon wilds found the Chinook Indians provided with robes made of skins of the mountain-beaver. From that time until recently but little accurate information has been available concerning the habits of this curious animal. Locally it is known by several other names, including “Sewellel,” “mountain boomer,” “boomer,” and, in the Olympic mountains, “chehalis.” The genus of mountain-beavers contains only a single species with several subspecies, all having a close superficial likeness in size and form to a tailless muskrat, except for their coarse, harsh fur. It is an exclusively North American type and, aside from a remote relationship to the squirrel family, has no kin among living mammals. It appears to be a sole survivor from some former age. As with the pocket gophers, its mode of life has developed powerful muscles about the head, front legs, and forepart of the body. The distribution of the mountain-beaver in Tertiary times extended through the Great Basin to North Dakota, but at present is closely restricted to the humid region between the crests of the Cascades and the Sierra Nevada and the Pacific coast, and from the lower Fraser River, British Columbia, south to the latitude of San Francisco Bay, California. [Illustration: WHITE-FOOTED MOUSE (Adult and Young) _Peromyscus leucopus_] [Illustration: BEACH MOUSE _Peromyscus polionotus niveiventris_] Within this superbly forested region this animal delights in locations that are cool and oozing with water, where, under the dense shade of an almost tropical undergrowth of shrubs, ferns, and other herbage, it constructs numberless tunnels and trails. These are sometimes in flats, but much more often along canyons and mountain slopes, among willow, alder, aspen, or other thickets, or even in the heavy coniferous forest. [Illustration: BIG-EARED ROCK MOUSE _Peromyscus truei_] [Illustration: BROWN RAT _Rattus norvegicus_ HOUSE MOUSE _Mus musculus_]