The body is long and moderately deep, scales are in a lateral line sixty-two to eighty. The head is long and quadrangle and is about four times in body length, with a small eye high on the head. An inferior mouth on a long blunt snout, lips are thick, and the lower lip is broad, fleshy and deeply incised. Dorsal fin is longer than high and the caudal is moderately long and forked. The color ranges from blackish to dark olive gray on back and a dusky lateral stripe on the side, with the belly yellowish to white.
Natural range is restricted to Western North America.
They can be found in the Peace River in Alberta, British Columbia, and the Sixes River in Oregon. The Large-scale Sucker is common in the Snake River upstream to Shoshone Falls. The sixth sucker species that is found in Idaho is the Mountain Sucker, Catostomus pjatyrbyndma. Their body form is slender and scales are small eighty to eighty-five in the lateral line. The head is short and concise, with a long snout and large ventral mouth which has a pronounced notch at each side.