105 Columbia Poached Rat
PSEUDOSTOMA DOUGLASII.--RICH. [Thomomys talpoides] COLUMBIA POUCHED-RAT. [Northern Pocket Gopher] PLATE CV.--MALES. P. Supra fusca, lateribus subrufis, ventre pedibusque pallidioribus, cauda corporis dimidio longiore.
CHARACTERS. Above, dusky brown; reddish on the sides; paler beneath and on the feet tail exceeding half the length of the body. SYNONYME. GEOMYS DOUGLASII. Richardson, Columbia Sand-Rat, Fauna Boreali Americana, p. 200, pl. 18 B. DESCRIPTION. Head, large and depressed; ears, short, ovate, extending beyond the fur nose, blunt; nostrils, small and round, separated by a line in the septum; they have a small naked margin. Mouth, of moderate size; lips, and space between the nose and upper incisors, covered with short hair; incisors strong, and slightly recurved; upper ones with a distinct furrow on the anterior surface, near their inner edge; cheek pouches, large, opening externally (like those of all the other species belonging to this genus), and lined on the inside with very short hairs. The pouches extend from beneath the lower jaw along the neck to near the shoulders; whiskers, short; body cylindrical, resembling that of the mole, and covered with short, dense, velvety fur; the tail, which is round and tapering, although at first sight appearing naked, is covered with hair throughout its whole length, but most densely near the root; legs short, and moderately robust; fore-toes short, the three middle ones united at their base by a skin, the outer one smaller and farther back; thumb, very small and armed with a claw; claws, sharp-pointed, compressed, and slightly curved; palms naked, and on the posterior part filled by a large, rounded callosity. The palms in this species are much smaller than in P. Bursarius; the hind-feet are rather more slender than the fore-feet, and their claws are decidedly smaller; soles of hind-feet, entirely naked, and without any conspicuous tubercles; heel, naked, and narrow; feet and toes, thickly clothed with hair extending to the nails. COLOUR. Incisors, dull orange; whiskers, nearly all white; upper surface of body, top of the head, and along the sides of the pouches, dusky-brown; sides, reddish-brown; edges of pouches, dark-brown; under surface of body, feet, and tail, pale buff; nails, yellowish-white. DIMENSIONS. Inches Lines Length of head and body, . . . . . . . . 6 6 Length of head, . . . . . . . . . . . 1 10 Length of tail (vertebrae), . . . . . . . 2 10 From point of nose to eye, . . . . . . . 0 11 From point of nose to auditory opening, . . . 1 8 Between the eyes, . . . . . . . . . . 0 7 From wrist joint to end of middle claw, . . . 1 0 HABITS. This species of Sand-Rat was first obtained by Mr. DAVID DOUGLAS, near the mouth of the Columbia river, since which, specimens have been sent to England by various collectors. According to Mr. DOUGLAS, the animal, "when in the act of emptying its pouches, sits on its hams like a Marmot or Squirrel, and squeezes its sacs against the breast with the chin and fore-paws." "These little Sand-Rats are numerous in the neighbourhood of Fort Vancouver, where they inhabit the declivities of low hills, and burrow in the sandy soil. They feed on acorns, nuts (Corylus rostrata), and grasses, and commit great havoc in the potato-fields adjoining to the fort, not only by eating the potatoes on the spot, but by carrying off large quantities of them in their pouches."--Fauna Boreali Americana, p. 201. GEOGRAPHICAL DISTRIBUTION. This species inhabits the valleys to the west of the Rocky Mountains, and seems to have been most frequently observed in about the latitude of the mouth of the Columbia River. Its probable range may extend as far as California to the south, and the Russian Possessions in the opposite direction. We have seen some mutilated specimens, which appeared to be of this species, obtained by a party in the western portion of New Mexico, but so dilapidated were they, that it was impossible to decide positively as to their identity, and they may have been skins of another species, called by Dr. RICHARDSON Geomys Umbrinus, which he was informed came from the southwestern part of Louisiana. GENERAL REMARKS. Mr. DOUGLAS informed Dr. RICHARDSON "that the outside of the pouches was cold to the touch, even when the animal was alive, and that on the inside they were lined with small, orbicular, indurated glands, more numerous near the opening into the mouth. When full, the pouches had an oblong form, and when empty they were corrugated or retracted to one third of their length." We presume this information is correct, although the mistake made by supposing the "inverted" pouches of some species of Pseudostoma, to be in their natural position (see the genus diplostoma of RAFFINESQUE, adopted by RICHARDSON), leads us to look with caution on any accounts of the pouches of our Sand-Rats from this source.