Differs from the other species of Echimys hitherto described by the extraordinary length of the tail. Upperparts rusty brown: cheeks, sides of the abdomen and outside of legs rusty. Chin, chest, belly and inside of legs dirty white. Woolly hairs on the upperparts rusty, intermixed with narrow flexible rigid hairs, rusty near the base, brown towards the tip. The colors of the upper and lower parts are sharply defined.