FEWKES] TANOAN EPOCH 283 
structed their fragile-walled habitations in a cavern, and as an en- 
largement of their numbers occurred they were obliged to construct 
the terraced pueblos called cliff-dwellings, with rooms closely ap- 
proximated and constructed in terraces. In the course of time these 
cliff-dwellers moved out of their caverns into the river valleys or to 
the mesa summits, carrying with them the terraced architecture, 
which, born in caverns, survived in their new environment. This 
explanation is of course hypothetical, but not wholly without a basis 
in fact, for we find survivals of the prepuebloan architecture scat- 
tered throughout the Southwest, especially on the periphery of the 
terraced house area, as well as in the area itself. The ancient ter- 
raced house architecture is confined to a limited area, but around its 
ancient border are people whose dwellings are characterized by 
fragile-walled architecture. These are the survivals of the pre- 
puebloan culture. 
The environmental conditions along the San Juan and its tribu- 
taries in Colorado and New Mexico render it a particularly favorable 
culture center from which the pure pueblo type may have originated, 
and although observations have not yet gone far enough to prove 
that here was the place of origin of the unit type, and therefore of 
pueblo culture, there are strong indications that a fable of the 
Pueblos, that they came from the caves in the north, is not without 
legendary foundation so far as their origin is concerned. 
The term “cliff-dwelling,’ once supposed to indicate a distinct 
stage of development, refers only to the site and is a feature inade- 
quate for classification or chronology. All cliff-dwellings do not 
belong to the same structural type. There is little similarity save in 
site between Spruce-tree House on the Mesa Verde, and Montezuma 
Castle in the Verde Valley; the former belongs to the “ pure pueblo 
type,” the latter to another class of buildings related to “ compounds ” 
of the tributaries of the Gila and Salt River valleys. 
