In the preceding pages the author has considered several different types of buildings, which, notwithstanding their variety in forms, have much in common and can be interpreted as indicating an identical phase of pueblo development. A comparative study of their distribution shows us that they occur in a well-defined geographical area. In comparison with stone buildings in other parts of the Southwestern States, this phase shows superior masonry. It is considered as chronologically antedating the historic epoch and post-dating an earlier, and as yet not clearly defined, phase out of which it sprung in the natural evolution from simple to complex forms. These buildings express the communal thought of the builders, since they were constructed by groups of people rather than by individuals. Architecture representing the thoughts of many minds is conservative, or less liable to innovation or departure from prescribed forms and methods. These community houses express the thought of men in groups at different times, and, so far as archeology teaches, are the best exponents of what we call contemporary social conditions, while pottery and other small portable objects, being products of individual endeavor, furnish little on social organization, or general cultural conditions of communities. Although determination of cultural areas built on identity of pottery often coincides with those determined by buildings, this is not always the case. Specialized culture areas determined by highly conventionalized designs on ceramics are localized, more numerous, and as a rule more modern. Hence a culture area determined by architectural features may include several subareas determined by pottery. The author has thought it possible to differentiate two distinct epochs or phases of house building in the upper part of the San Juan drainage, viz. the early and the middle stages of development. There are included in the early condition certain crude architectural efforts similar to the non-Pueblos represented in regions adjoining the Pueblo area. This early condition, though not clearly defined, is beginning to be revealed by intensive studies of the so-called slab house dwellings and isolated brush houses. Evidences of this stage have been found in several localities, as on McElmo Bluff, or combined with walls of what may be called true pueblo buildings. The differences between some of the buildings of the early stage and those of the aborigines in southern California, or of the Utes and Shoshonean tribes, are slight; resemblances which point to relations are not considered in detail.