They resemble Chinchillas (to which they are closely related) in appearance but have a body-structure more like a rat. Bennett's Chinchilla Rats are medium-sized (head-body length 150-250 mm), and have a rat-like body with a long pointed nose, large rounded ears, and large eyes. Their legs are unremarkable. The forefeet have 4 digits and the hindfeet 5. Stiff hairs project beyond the nails of the middle hind digits and probably serve as a comb. The nails are weakly built. The tail is shorter than the head and body, cylindrical, and well-furred.

They are probably herbivorous, but their diets, like most other aspects of their biology, are poorly known.

The Bennett's Chinchilla Rat is known for its luxurious fur, which resembles the fur of the true chinchilla. They make their homes in rock crevices and underground tunnels. They are social animals that form small colonies and they communicate with grunts, squeaks, and gurgles.

They occur in rocky areas and thickets to around 5000 m elevation. They are found in Chile from Copiapo to the area of Rio Biobio.