Several of these ruins were described and figured by Mr. Warren K. Moorehead as “The Great Ruins of Upper McElmo Creek” in the Illustrated American for July 9, 1892, the sixth of a series of articles under a general title “In search of a Lost Race.” He gives descriptions of a “cave shelter” found near Twin Towers, Square Tower in “Ruin Canyon,” a building (Hovenweep Castle), and the tower at the junction of the North and South Forks of Ruin Canyon. This paper is accompanied by a map of Ruin Canyon by Mr. Cowen. In Moorehead’s discussion of these remains, individual towers and other ruins are designated by capital letters, A-V, to some of which are also affixed the names “Hollow Boulder,” “Twin Towers,” “Square Tower,” etc. Details of structure and measurements of the more striking buildings and a discussion of certain features of structure, some of which will be considered later under individual ruins, are likewise given. The most important general article yet published on the prehistoric remains of the region here considered is by Dr. T. Mitchell Prudden,[4] who also mentions several of the ruins here treated. His most important contribution is a description of what he calls the “unit type,” which he recognized as a fundamental structural feature in the pueblos of this region. He also showed that the kiva in Montezuma Valley villages is identical with that of cliff-dwellings in the Mesa Verde, and emphasized, as an important feature, the union of the tower and the pueblo, a characteristic of the highest form of pueblo architecture. Doctor Prudden has followed his comprehensive paper above mentioned with an account[5] of the excavation of one of the mounds at Mitchell Spring in which he adds to our knowledge of the structure of his “unit type.” In “A Further Study of Prehistoric Small House Ruins in the San Juan Watershed,”[6] Doctor Prudden has furnished important additional data which shows the uniformity of the unit type over a large area of the San Juan drainage. [4] The Prehistoric Ruins of the San Juan Watershed in Utah, Arizona, Colorado, and New Mexico., Amer. Anthrop., n. s. vol. v, no. 2, 1903. [5] The Circular Kivas of Small Ruins in the San Juan Watershed. Amer. Anthrop., n. s. vol. xvi, no. 1, 1914. [6] Memoirs Amer. Anthrop. Asso., vol. v, no. 1, 1918. The following among other prehistoric remains in the district mentioned or described by Doctor Prudden are covered by the author’s reconnoissance: 1. Ruins at Dolores Bend (Escalante Ruin). 2. Wolley Ranch Ruin. 3. Burkhardt Ruin (Mud Spring Village). 4. Goodman Point Ruin. 5. Unnamed ruin west of Goodman Lake. 6. Ruin at junction of McElmo and Yellow Jacket. 7. Group on Yellow Jacket nearly opposite mouth of Dawson Canyon (Davis or Littrell Tower). 8. Surouaro. 9. Cannonball Ruin. 10. Towers and buildings of Ruin and Bridge Canyons. 11. Pierson Spring Ruin. 12. Bug Spring Ruins.