Coloration of the upper parts ranges from blackish brown to grayish and sandy, with tinges of buff. The underparts and the feet are white or buffy, and occasionally there is a rusty tinge on the nape and crown. The tail of C. albipes is distinctly bicolored, dark brown above and white below for its entire length, whereas the tail of C. penicillatus is wholly black or has a terminal black tip. The tail is usually uniformly haired throughout and tufted at the tip. Conilurus has fairly large ears and a moderately long hind foot.
Females have four mammae.
C. penicillatus is nocturnal in habit, sleeping by day in hollow trees and limbs, where it constructs a comfortable, well-lined nest of pieces of vegetation. In the evenings it may run along the edge of the surf, apparently feeding on matter that is thrown up on the beach by the waves. Favored habitats were near the beach in either grassy or sand dune areas. The animals were nocturnal, and both arboreal and terrestrial activity was noted. Cited observations indicate that the young cling tenaciously to the nipples, even when the female scampers about away from the nest.