Thus we have in the southwest a most fortunate situation for the archæologist. The ruins are of such a character and so situated as to resist the action of the weather, and the climate singularly adapted to the preservation of not only the buildings, but also the more perishable remains. So completely did the indigenous culture overspread the area in question that there is not a waterway of any consequence from the Pecos to the Colorado and from the San Juan to the Gila that is without numerous ruins. They are distributed along not less than a hundred valleys in New Mexico, Arizona, Colorado and Utah. In a paper and map prepared recently for the use of the Department of the Interior, I have indicated the distribution of the ruins over the four general drainage-areas, the Rio Grande, the San Juan, the Little Colorado, the Gila, and as a tentative scheme have shown how they may be grouped into twenty archæological districts. (This grouping has no ethnological significance.) The districts are grouped as follows: I. The Rio Grande Basin: 1. Pajarito Park district. 2. Pecos Pueblo district. 3. Gran Quivira district. 4. Jemez district. 5. Acoma district. II. The San Juan Basin: 1. Aztec district. 2. Mesa Verde district. 3. Chaco Cañon district. 4. Cañon de Chelly district. 5. Bluff district. III. The Little Colorado Basin: 1. Tusayan district. 2. Flagstaff district. 3. Holbrook district. 4. Zuñi district. IV. The Gila Basin: 1. Rio Verde district. 2. San Carlos district. 3. Lower Gila district. 4. Middle Gila district. 5. Upper Gila district. 6. San Francisco River district. Following is a brief memorandum showing the extent of each district: I. RIO GRANDE BASIN. This culture area, lying wholly in New Mexico, embraces the Rio Grande Valley with its tributaries from Ojo Caliente on the north to Socorro on the south and from Acoma on the west to the plains east of the Manzano Mountains. II. SAN JUAN BASIN. The ruins of the San Juan Basin consist of both large and small communal houses and true cliff dwellings in great numbers. They are scattered in numerous, irregular groups over the contiguous portions of New Mexico, Colorado, Utah, and Arizona. All the ruins of the San Juan and its tributaries have suffered much from destructive collectors. III. LITTLE COLORADO BASIN.