Two centers of distribution of cliff houses occur in our Southwest: those of the upper tributaries of the Colorado in the north and the cliff houses of the affluents of the Salt and the Gila in the south. The watershed of the Rio Grande is, so far as is known, destitute of this kind of aboriginal dwellings. Between the two centers of distribution lie the pueblos of the Little Colorado and its tributaries, the home of the ancestors of the Hopi and the Zuñi. The many resemblances between the cliff houses of the north and those of the south indicate that the stage of culture of both was uniform, and probably the same conditions of environment led both peoples to build similar dwellings. All those likenesses which can be found between the modern Zuñi and the Hopi to the former cliff peoples of the San Juan region in the north, apply equally to those of the upper Salado and the Gila and their tributaries to the south; and so far as arguments of a northern origin of either, built on architectural or technological resemblances, are concerned, they are not conclusive, since they are also applicable to the cliff peoples of the south. The one important difference between the northern and the southern tier of cliff houses is the occurrence of the circular kiva, which has never been reported south of the divide between the Little Colorado and the Gila-Salado drainage. If a kiva was a feature in southern cliff houses, which I doubt, it appears to have been a rectangular chamber similar to a dwelling room. The circular kiva exists in neither the modern Hopi nor the Zuñi pueblos, and it has not been found in adjacent Tusayan ruins; therefore, if these habitations were profoundly influenced by settlers from the north, it is strange that such a radical change in the form of this room resulted. The arguments advanced that one of the two component stocks of the Zuñi, and that the aboriginal, came from the cliff peoples of the San Juan, are not conclusive, although I have no doubt that the Zuñi may have received increment from that direction. Cushing has, I believe, furnished good evidence that some of the ancestors of the Zuñi population came from the south and southwest; and that some of these came from pueblos now in ruins on the Little Colorado is indicated by the great similarity in the antiquities of ancient Zuñi and the Colorado Chiquito ruins. Part of the Patki people of the Hopi went to Zuñi and part to Tusayan, from the same abandoned pueblo, and the descendants of this family in Walpi still recognize this ancient kinship; but I do not know, and so far as can be seen there is no way of determining, the relative antiquity of the pueblos in Zuñi valley and those on the lower Colorado.