Where exceptionally large blocks of stone are available they have been utilized in an upright position, and occur at greater or less intervals along the thin walls of dry masonry. An example of this use was seen in a garden wall on the west side of Walpi, where the stones had been set on end in the yielding surface of a sandy slope among the foothills. A similar arrangement, occurring close to the houses at Ojo Caliente, is illustrated in Pl. XCII. Large, upright slabs of stone have been used by the pueblo builders in many ways, sometimes incorporated into the architecture of the houses, and again in detached positions at some distance from the villages. Pls. XCIII and XCIV, drawn from the photographs of Mr. W. H. Jackson, afford illustrations of this usage in the ancient ruins of Montezuma Canyon. In the first of these cases the stones were utilized, apparently, in house masonry. Among the ruins in the valley of the San Juan and its tributaries, as described by Messrs. W. H. Holmes and W. H. Jackson, varied arrangements of upright slabs of stone are of frequent occurrence. The rows of stones are sometimes arranged in squares, sometimes in circles, and occasionally are incorporated into the walls of ordinary masonry, as in the example illustrated. Isolated slabs are also met with among the ruins. At K’iakima, at a point near the margin of the ruin, occurs a series of very large, upright slabs, which occupy the positions of headstones to a number of small inclosures, thought to be mortuary, outlined upon the ground. These have been already described in connection with the ground plan of this village.