THE POUCHED RATS. 123 



bursarius), inhabits the whole valley of the Mississippi, and extends northwards into Canada. It 

 reaches the foot of the Rocky Mountains in Colorado, but is not known to occur west of that 

 range. It is also found in Texas. This Pouched Rat, like the rest of its genus, has the incisors 

 broad and the upper ones deeply grooved ; but in addition to the ordinary deep groove it has a 

 fine line close to the inner margin of each of these teeth. Its form is stout and clumsy, but its 

 coat is beautifully soft and velvety, like that of the Mole, but of a dull reddish-brown colour, with 

 the feet and tail white. The average length of an adult specimen is from seven to eight inches, 

 and the tail is two or three inches long. This organ is clothed with hair nearly to the tip. 



Like the Mole, this animal lives in burrows, which it makes in all directions in the ground, 

 throwing out as it proceeds heaps of earth, which exactly resemble ordinary mole-hills. To enable 

 it to perform these labours the claws of the fore feet are exceedingly powerful ; and to adapt it the 

 better to its subterranean existence, the eyes are very small, and the external ears are wanting. Its 

 digging operations have generally the same object as 

 those of the Mole namely, the search for food. The 

 tunnel is carried along not far from the surface of the 

 ground, and the roots of any plants that lie in its 

 covirse are bitten off and devoured by the little miner. 

 Besides the runs, the Pouched Rat digs himself a con- 

 venient dwelling in the shape of a chamber hollowed 

 out xmder the roots of a tree, access to which is 

 gained by a somewhat spiral descending passage. 

 This chamber, which is usually at a depth of four or 

 five feet, is comfortably lined with soft grass, and the 

 nest in which the female brings forth her young is a 

 cavity of the same kind, but surrounded by circular SKULL OF THE MEXICAN POUCHED HAT. 



passages, from which, like that of the Mole, other pas- 

 sages branch off. One of these, according to Gesner, leads from the nest to a large store-chamber filled 

 with nuts, seeds, and roots, among which the potato was found to play an important part. These pro- 

 visions are carried to the store-house in the great cheek-pouches, which the animal is said to fill by the 

 aid of its tongue, and to empty with the fore paws. This Pouched Rat does much damage in 

 cultivated ground by attacking the roots of both plants and trees, sometimes destroying a great 

 number of the latter in a few days. The female produces from five to seven young at the end 

 of March or the beginning of April. The other species of Geomys closely resemble this in their 

 habits. 



Of the second genus belonging to this sub-family (TJiomomys) Dr. Coues admits only two 

 species, one of which, however, occurs under three named forms. They may be distinguished from 

 the species of Geomys by their having the upper incisors plain, without grooves. 



The NORTHERN POCKET GOPHER (Thomomys talpoides), with its sub-species, ranges over nearly the 

 whole of North America from the Hudson's Bay Territory to California and New Mexico. The three 

 forms are for the most part in accordance with geographical distribution. A small species (Thomomys 

 clusius) has been obtained in the Rocky Mountains. 



The HETEROMYIN^E (forming the family Saccomyidse of Dr. Coues, although he does not accept 

 the genus Saccomys) are more slender and delicate in form than the Geomyinse, and have the hind 

 limbs and tail elongated, the former, indeed, being converted into leaping organs like those of 

 the Jerboas and Kangaroos. The eyes and ears are larger, and the animals are in every respect 

 adapted to life in the open, while the Geomyinse, on the contrary, are subterranean in their 

 habits. The hair in the present family is coarse and harsh, sometimes even spiny. In skeletal 

 characters we find a similar alteration. The incisors are narrow ; the skull is delicate, with its angles 

 rounded off, and the mastoid bones form a considerable part of the roof of the cranial cavity ; the 

 zygomatic arches are slender ; and, the lower root of the maxillary process being undeveloped, the 

 infra-orbital opening is not defined. As in the Jerboas, the cervical vertebrae are sometimes anchylosed. 

 Like the Geomyinse, these animals are confined to America, and chiefly limited to the Southern 

 United States and Central America, although some of the species occur as far north as the Columbia 



