CLASS I. MAMMALIA: OEDEE 7. RODENTIA. 459 
Drummond's Neotome, N. Drummondii, is nine inches long, yellowish-brown in winter and 
ash-color in summer, and is found in the Eocky Mountains from 30° to 70° north latitude. Gray 
makes of this a genus which he calls TEONOMA, which is only an anagram of JSFeotoma. 
The Genus OXYMYCTEEUS : Oxymycterus^ contains several South American species, 
among which are the 0. nasu tus, of the La Plata country, and 0. scalops, of Chili. 
The Genus AKODON comprises the A. BoUviense^ of Bolivia and Peru. 
The Genera EEITHEODON, PHYLLOTIS, and ELIGMOr>ONTIA embrace various South 
American species, but of no interest or importance. The Genus HOLOCHILUS includes the 
Brazilian Eat, the Mus Brasiliensis of Geotfroy, which is of the size of the Brown Eat. The 
Yellow Eat, Mus lutescens^ resembles the preceding. The Pilobi Eat, Mus pilorides, is still 
larger, and is ill many respects peculiar. It is black above and white below, and is found not 
only in Brazil but in the West Indies. 
We now come to the Ncav Holland Muriens. The Genus HAPALOTIS presents several spe- 
cies. The JI. albi2oes is nearly of the size of a rabbit, but of a mouse-like form, and is chiefly 
found in New South Wales. The H. Gouldii and H. melanura are of New Holland. 
Genus HYDEOMYS : Hydromys. — Of this there are two species, the Yellow-bellied Hy- 
DROMTs, H. chrysogaster, and the White-bellied Hydromys, S. leucogaster. Both are of a 
chestnut color above, but one is yellow and the other white, beneath. They are found along the 
Swan Eiver. 
MUS ALBOCINEEEUS. 
Beside the animals forming the two preceding genera, Australia has been found to possess a 
number of veritable species of the Mus genus. The distinguished naturalists Gray and Gould 
have given us descriptions of several, among which we may mention the Mus albocinereus, Mus 
AustraliSy and Mus Grayii. These are all of small size. 
Genus PITHECHEIEUS : Pithecheirus. — This includes one animal, the P. melanurus, which 
has puzzled the naturalists, inasmuch as it resembles alike the rats and the opossums, yet cannot be 
admitted into the department of either, as it has not the feet of the former nor the tail of the lat- 
ter. Its body is a uniform brown color, the tail being black. It is the size of a large rat, and is 
found in India and some of the Asiatic islands. 
Fossil Eodentia. — The number of known species of Eodentia now existing is at least six hun- 
dred ; from the fossil remains which have been discovered of Hares, Porcupines, Agoutis, Cavies, 
Dormice, Spermophiles, Jerboas, Gerbils, Field-Mice, Lemmings, Water-Eats, &c., we have rea- 
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