As our studies are morphological, dealing with forms rather than sites of towers, little attention need be paid to their situation on bowlders, in cliffs, or at the bottoms of canyons. The majority of the castellated ruins considered in the following pages are in the proposed Hovenweep National Monument, but there are others in the main Yellow Jacket and its other tributaries. [44] The tower figured by Prudden (Amer. Anthrop., n. s. vol. v, no. 2, pl. xviii, fig. 2) as a “round tower” is really semicircular, as shown in the ground plan (fig. 14) here published. [45] Ibid., pp. 241, 263, 273. HOVENWEEP DISTRICT The name Hovenweep (“Deserted Valley”) is an old one in the nomenclature of the canyons of southwestern Colorado and formerly (1877) was applied to the canyon now called the Yellow Jacket, but at present is limited to one of the tributaries. The name is here used to designate an area situated just over the Colorado State line, in Utah, part of which it is hoped will later be reserved from the public domain and made a monument to be called Hovenweep National Monument. The ruined castles and towers in this district are marvelously well preserved, considering their age and imperfect masonry. We can determine their original appearance with no difficulty and use them in reconstructing the possible forms of more dilapidated ruins, now piles of débris. The best castles and towers known to the author are localized in three canyons: (1) Square Tower Canyon, (2) Holly Canyon, (3) Hackberry Canyon. There are, of course, other castles and towers in the Yellow Jacket-McElmo region, but there is no locality where so many different forms appear in equal numbers in a small area. RUIN CANYON The Old Bluff Road from Dolores diverges southward from that to Monticello at Sandstone post office and passes a pile of rocks visible from the road on the Ruin Canyon long before it reaches Square Tower Canyon (fig. 6). This large ruin is situated on the east rim and under it in the side of the cliff are fairly well-preserved cliff-houses. Other ruins with high standing walls were reported in Ruin Canyon but were not visited. The duplication of names of canyons in this district is misleading. Names like Ruin Canyon are naturally applied to canyons in which there are ruins. When the author learned at Dolores of Ruin Canyon, he supposed it was a tributary of the Yellow Jacket or McElmo, but while the canyon known to cowboys at Dolores by this name has large ruins on its rim, it is not the “Ruin Canyon” to which attention is now directed. The duplication of names has led me to retain the name Ruin Canyon for one and to suggest the name Square Tower Canyon for the other. [Illustration: FIG. 6.—Square Tower Canyon.]