The " black mouse " or Carson field mouse (Microtus montanus) is found throughout Nevada, as well as in Utah, north-eastern California, and eastern Oregon; it multiplies rapidly under favourable conditions, and at times causes serious injury to crops.
There are several varieties of grasshopper mice (Orychomys), white-footed mice (Peromyscus), harvest mice (Reithrodontomys), rice-rats (Oryzomys), wood-rats (Neotoma), voles (Microtus), &c. Bats inhabit caves in Burnet, Williamson, Lampasas, Gillespie and other counties.
The peculiar odour evolved by many rodents is due to the secretions of special glands, which may open into the prepuce, as in Mus, Microtus and Cricetus, or into the rectum, as in Arctomys and Thryonomys, or into the passage common to both, as in the beaver, or into pouches opening near the vent, as in hares, agoutis and jerboas.
In the circumpolar Evotomys (represented in England by the red-backed field-mouse) and the nearly allied North American Phenacomys, the molars develop roots in old age; but in Microtus (which includes the water-rat, and is circumpolar) they are rootless throughout life, the genus being' one of the largest in the mammalian class (see Vole).
The first of these is the common shoa 1 tailed field-mouse, or "field-vole," Microtus agrestis, which belongs to the typical section of the type genus, and M S is about the size of a 343 mouse, with a short stumpy body, and a Upper and Lower Molars of the Water-Rat tail about one-third the (or Water-Vole), Microtus amphibius.
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