Studies of middle Paleozoic history in western America have long been delayed. For the past 50 years efforts of stratigraphers on the Pacific Coast have been devoted largely to investigation of Mesozoic and Cenozoic strata, good outcrops of which are found in the vicinity of several western centers of geologic research. Moreover, growing importance of geology in the petroleum industry has given vital encouragement to study of the younger strata. Remote and somewhat difficult of access, the Paleozoic areas have received but small share of the attention they justly deserve. Conclusions regarding the older systems have thus remained speculative in...