The guard hairs and underfur differ in different species (see figs. 35-37).
The width of a hair in the underfur is of no taxonomic significance, in that individual variation exceeds that between species.
The sides and underparts are lighter, due primarily to much less black in the underfur.
Color: Darker throughout, especially on dorsal surface due to more black of the underfur; underparts deeper buff.
In mice in the earlier stages of adulthood, underfur of the dorsum is buffy at the tips and gray basally.
More than 200 impression slides and whole mounts of guard hair and underfur were prepared.