464 ZOOLOGY. 
believe these animals always for that purpose resort to holes in the sides of 
ponds, sluggish streams, or dykes.” | 
The arvicoline Muridz were present in the tertiary fauna. . Several 
species of Arvicola or Hypudcus are mentioned and described from conti- 
nental Kurope. 
The genus Stenofiber, referred to the arvicolines by some and to beavers 
by others, has been established upon a skull found in the middle tertiary 
geds of Auvergne. Its forms are intermediate between the beaver and the 
musk-rat. 
Sub-fam. 4. Spalacina, of which there are no representatives in North 
America, is a small group composed of but thirteen species, distributed into 
seven genera, as follows: Ahizomys, six species, Asiatic and African ; 
Tachyoryctes and Heterocephalus, each one species, both African ; Ellobius, 
two species, Huropean and Asiatic; Ommatostergus and Spalax, each one 
species, both in France; and Siphneus, one species, in Siberia. 
The genus Spalax (the rat-moles) has very short legs, each foot provided 
with five toes and as many flat and slender nails. The tail is very short 
or completely wanting, and the same observation applies to the external 
ear. They live under ground like the moles, raising up the earth like them, 
although provided with much inferior means for dividing it; but they subsist 
on roots only. The blind rat-mole (S. typhius) is a very singular animal, 
which, from its large head, angular on the sides, its short legs, and total 
absence of a tail and of any appendage externally, has the most shapeless 
physiognomy. In the opinion of some writers, this should be the animal 
alluded to by the ancients, when they spoke of the mole as being perfectly 
blind. 
Sub-fam. 5. Murina, has a greater number of representatives in the old 
than in the new world. The genera into which they are distributed amount 
to not less than twenty-eight to thirty, and the species to more than two 
hundred. There are comparatively very few in North America, where the 
genera Mus, with eight species; Neotoma, with two; and Sigmodon and 
Hesperomys, with only one, in all twelve species, represent Murina. 
The Asiatic and African mice and rats are distributed into the genera 
Isomys, Akomys, Golunda, Vandeleuria, Nesokia, Dendromys, Pithechezr, 
Cricetomys, Phlaeomys, Psammomys, Malacothrix, Euryotis, Mystromys. The 
genera Hapalotis and Hydromys are Australian. In South America we find 
forty-five species of Hesperomys, the genera Oxymycterus, Calomys, Akodon, 
Drymomys, and Reithrodon, with a few only. The European species belong 
to the genera Sminthus, Gerbillus, and Cricetus, which have also representa- 
tives in Asia and northern Africa. 
The genus Mus (rats and mice) is distributed throughout the whole sur- 
face of the globe. It is characterized by three moiars on each side above 
and below, the anterior of which is the largest; its crown is divided into 
blunt tubercles, which, by being worn, give it the shape of a disk, sloped in 
various directions; the tail is long and scaly. The ears oblong or round, 
nearly naked. The common mouse, Mus musculus (pl. 118, fig. 8), 
originally from the East, has been introduced into America with the white 
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