CLASS I. MAMMALIA: ORDER V. RODENTIA.. 419 
jerboa, with a tail long and tufted at tlie end, and living on vegetable food. Their dbeek-pouches 
open externally. 
Phillips's Pouched Gerboa-Mouse, J). Phillips ii^ is aboiit as large as the clnp-squirrel, having 
a bodj^five inches long and a tail six and a half inches; the color is light-brown above and white 
beneath. The whiskers are rigid and numerous, hind-legs very long, the fur silky, the eyes bright, 
the form and appearance like a very minute kangaroo. It hops about on its hind-legs, often 
taking considerable leaps. It lives in holes in the arid plains of Sonora and Southern California, 
seeming to prefer stony slopes, and frequently comes around the tents of travelers with a sort of 
confiding gentleness and familiarity. It seems to go forth chiefly at nightfall. 
Several other species of this genus have been recently discovered. Ord's Pouched-Mouse, I). 
Ordii, is dark-brown above and white beneath; ihe tail is short and tufted at the end; it is a 
little smaller than the preceding, and is found in the ^'icinity of El Passo. 
The Agile Dipodomys, D. agilis^ is ten and a half inches long, the tail six and a half; the 
color a yellowish-brown above; on the sides and beneath it is white; eyes large; large external 
cheek-pouches ; hind-legs very long. It is a beautiful species, leaps with surprising agility, some- 
times ten feet at a bound. It forms extensive burrows, and is difficult to be captured. It abounds 
in the cnltivated fields and vineyards near Puebla de los Angelos, California, 
Hermann's Dipodomys, D. Hermannii, is found in the Sierra Nevada, but is little known. 
Genus MACROCAULUS : Macrocauhis^ presents a single species, J/, halticiis ; this has the 
body four inches, and the tail six inches long. It is found in Mexico, but has not been fully de- 
ascribed. 
JERBOAS. 
THE DIPODID^ 
This curious family embraces three tribes of small animals : the Jerboas, Pedetiens, and Cteno- 
dactyliens. 
THE JERBOAS OR JERBOID^. 
This tribe has been divided into several genera by some naturalists, as Scirtopodes, Scirtomys^ 
