THE SAND ROLLERS Family XXIV. Percopsidae This small family is of special interest because it combines with ordinary Salmonoid characters the structure of the head and mouth of the Percoids, as may be seen by the accompanying illustration. Only 2 genera known, each with a single species. Percopsis guttatus, the common sand roller or trout perch, is found in lakes and suitable streams from Lake Champlain and the Delaware River, west to Kansas and Assiniboia. It prefers cold, clear waters, and is most abundant in the Great Lakes, particularly in Lakes Michigan and Superior. It spawns in the spring, at which time it runs into tributary streams in great numbers. Mr. Andrew Halkett, Naturalist of the Department of Marine and Fisheries, Ottawa, informs us that immense numbers are seen in the Moira River every spring. Though reaching a length of only 6 or 8 inches, the sand roller takes the hook readily, and is used as a pan-fish. We have seen boys on the Chicago piers catching them in great numbers. Columbia transmontana is known only from the Umatilla, River at Umatilla, Oregon, and the Walla Walla River at Wallula, Washington, both places in the Columbia River Basin.