Tail rather short, clothed with short depressed hairs.
The spines are mixed with long soft hairs.
They include three genera, of which the first is represented by the Canadian porcupine (Erethizon dorsatus), a stout, heavily-built animal, with long hairs almost or quite hiding its spines, four frontand five hind-toes, and a short, stumpy tail.
The gall is cup-shaped, and its outer surface is crumpled and covered with small warts and hairs.
They are of a lighter build than the ground-porcupines, with short, close, many-coloured spines, often mixed with hairs, and prehensile tails.