The fur varies exceedingly in character, - in some, like the chinchillas and hares, being fine and soft, while in others it is more or less replaced by spines on the upper surface, as in spiny rats and porcupines; these spines in several genera, as Xerus, Acomys, Platacanthomys, Echinothrix, Loncheres and Echinomys, being flattened.
None of the members of the typical sub-family extend into India, where the group is represented by Platacanthomys, typifying the sub-family Platacanthomyinae, characterized by the absence of premolars; the other being the Chinese Typhlomys.
Though usually more or less cylindrical or circular in section, hairs are often elliptical or flattened, as in the curly-haired races of men, the terminal portion of the hair of moles and shrews, and conspicuously in the spines of the spiny squirrels of the genus Xerus and those of the mouse-like Platacanthomys.
A second subfamily is represented by the Indian Platacanthomys and the Chinese Typhlomys, in which there are only three pairs of cheek-teeth; thus connecting the more typical members of the family with the Muridae.