Many artificial reservoirs dating to prehistoric times were observed in the area covered by the author’s reconnoissance. These fall into two well-marked types, one form being a circular depression, apparently excavated and sometimes walled up with earth or stones. The other form was not excavated by man, but the sloping surface of rock was surrounded on the lowest level by a bank of earth, forming a dam or retaining wall. Both types of reservoirs are commonly formed near some former center of population, but sometimes occur far from mounds, wherever the surface of the land has a convenient slope and the water can be compounded by a retaining wall. The height of the bank that holds back the water of these prehistoric reservoirs has been increased in some cases by stockmen; the walls of others still remain practically the same height they were when constructed by the aborigines. One of the best examples of the second type of reservoir, the retaining wall of which is shown in plate 32, _a_, is crossed by the road to Bluff City near the ruins in Holly Canyon, not far from Picket corral. A few miles north of this reservoir, at the edge of the cedars, the road crosses another of these ancient reservoirs, whose retaining bank has been considerably increased in height by stockmen. The ancient reservoir at Bug Mesa covers fully 4 acres, and the reservoir near Goodman Point Ruin is almost as large, and, although somewhat changed from its aboriginal condition, is still used by farmers dwelling in the neighborhood. The latter belongs to the first type; the former to the second. Reservoirs of one or the other type are generally found in the neighborhood of all large heaps of rocks, the so-called mounds that indicate the former existence of pueblos. The reservoir of the Mummy Lake village on the Mesa Verde belongs to the excavated type. PICTOGRAPHS