124 NATURAL HISTORY. 



River and Hudson's Bay, and one is found in Trinidad. By American writers they are called 

 " Pocket Mice." 



PHILLIPS'S POCKET MOUSE, also known as the Kangaroo Rat (Dipodomys Phittipsii), is one of the 

 best known species of this group. It is an elegantly formed little creature, about four inches long, 

 with a slender tail nearly six inches in length. Its colour above is mouse-brown, white beneath ; the 

 sides of the body have some white streaks, especially one from the ear towards the shoulder, and one 

 on the thigh running towards the root of the tail ; the tip of the tail is also white. This is a Cali- 

 fornian species, but extends throughout the Pacific region of the United States. It is represented 

 in the Rocky Mountains by a rather larger and stouter form, with smaller ears and a shorter tail 

 (Dipodomys Ordii), which is generally regarded as distinct, but is placed by Dr. Coues as a sub- 

 species. The habits of the species are comparatively little known, but they appear to live in the 

 most desert places they can find, the barren spots on which the only plants that seem to flourish are 

 the great mis-shapen cactuses. They dwell in holes under rocks and stones, from which they emerge 

 at sunset, and hop about gaily after the fashion of little Kangaroos. The places in which these 

 Pocket Mice are found are so bare of vegetation and destitute of water, that it is difficult to 

 imagine how they contrive to exist. In all probability they pick up a scanty living in the shape 

 of roots and grasses, especially seeds, carrying a supply for the day into their holes in their great 

 cheek-pouches. 



The YELLOW POCKET MOUSE and the LEAST POCKET MOUSE (Cricetodipus flavus and parvus) are 

 very minute creatures, only about two inches long in the head and body. The tail is longer than the 

 head and body in the latter, shorter in the former species, and the colour of the fur in both is a pale 

 buff. These species are found in the Rocky Mountains and the region west of that range to the 

 Pacific, the latter being inhabited by the second of the above species. Several species of the genus 

 Heteromys inhabit Central America, and one is found in the island of Trinidad. Nothing appears 

 to be known of their habits. 



From these we pass as by a natural transition to 



FAMILY X. DIPODID^ (THE JERBOAS). 



The JERBOAS are a more extensive and much more widely distributed family of hopping Rodents. 

 In these we find the organisation for jumping brought to greater perfection than in any other group. 

 The body is light and slender, the hind limbs much elongated, the fore limbs veiy small, and the tail long 

 and usually tufted at the end. The number of toes on the hind feet varies from three to five, and the 

 metatarsal bones are very often united so as to form what is called a " cannon bone " in the Horse. The 

 incisor teeth are compressed ; the molars sometimes four, but usually three in each series, rooted or root- 

 less, not tuberculate ; the infra-orbital opening is rounded and 

 very large, and the zygomatic arch slender. The great home 

 of these animals is the vast steppe region which stretches 

 from South-eastern Europe across the greater part of Central 

 Asia, but they extend southwards round the eastern extremity 

 of the Mediterranean, through Syria and Arabia to Egypt 

 and Africa, over a great part of which they are found, and 

 eastward to India, Afghanistan, and Ceylon. A single species 

 occurs at the Cape of Good Hope ; and another is found in 

 North America. We may commence by noticing this last 



SKULL OF THE CAPE JUMPING HARE. species, as it not only makes the nearest approach to those 



of preceding families, especially the Muridae, but differs from 



the rest of the Jerboas in characters of such importance, that Dr. Coues maintains its right to form a 

 separate family (Zapodidce). 



The AMERICAN JUMPING MOUSE (Zapus* hudsonius) has a wide range, extending across 



* Dr. Coues has proposed this generic name for the American Jumping Mouse, as the names Jaculus and Mer tones, 

 given to the genus by various authors, had been previously used for other groups. 



