The following towers can be identified from his figures:[7] 1. “Square building opposite mouth of Dawson Creek.” Prudden, pl. xviii, fig. 2. (This building is not square, but semicircular.) 2. Cannonball Ruin. Prudden, pl. xxi [xxii]. 3. “Small tower-like structure ... at the head of Ruin Canyon, in the Yellow Jacket group.” Prudden, pl. xxiii, fig. 2. (This building is not in Ruin Canyon, but in Holly Canyon.) 4. “Tower ... about the head of Ruin Canyon.” Prudden, pl. xxiii, fig. 1. (This is the most eastern of the Twin Towers, but not about the head of the canyon.) 5. Sand Canyon Tower. Prudden, pl. xxiv, fig. 2. Although mainly devoted to descriptions of the cliff-houses of the Mesa Verde, Baron G. Nordenskiöld’s “Cliff-Dwellers of the Mesa Verde” discusses in so broad a manner the relationship of pueblo ruins and cliff-houses that no student can overlook this epoch-making work. In fact, Nordenskiöld laid the foundations for subsequent students of pueblo morphology, although some of his comparisons and generalizations were premature because based on imperfect observations which have been superseded by later investigations. The partial excavation of the excellent ruin at the head of Cannonball Canyon by S. G. Morley[8] sheds considerable light on the morphology of prehistoric buildings in the McElmo district. Unfortunately no attempt was made by him to repair the walls of this ruin for permanent preservation, but it is not too late still to prevent their further destruction and preserve them for future students and visitors. Morley’s description of the buildings is accompanied by good photographs and a ground plan. He brought to light in this ruin examples of the characteristic unit type kiva. [7] Amer. Anthrop., n. s. vol. v, no. 2, 1903. [8] The Excavation of the Cannonball Ruins in Southwestern Colorado. Amer. Anthrop., n. s. vol. x, no. 4, 1908. The latest work on the McElmo Ruins, one part of which has already appeared, is a joint contribution by Morley and Kidder.[9] In this publication accurate dimensions and sites of ruins in the McElmo and Square Ruin Canyons are given, with other instructive data. Morley and Kidder have designated the ruins by Arabic numbers, and in a few instances by names. The author has preserved these numbers so far as possible in his account. The following ruins in Ruin Canyon and neighboring district covered by this reconnoissance are described by Morley and Kidder: