72 NEW MEXICO GEOLOGICAL SOCIETY THIRTEENTH FIELD CONFERENCE DEVONIAN CONODONTS IN ARIZONA

found along Pinal Creek north of Globe with the already well known fauna at Rockford, Iowa. The following year the same author examined brachiopods collected from the section at Bisbee by F. L. Ransome and correlated them with the Rockford fauna and fossils from the basal Chemung of New York. He interpreted Theodossia [ Spirifer] hunger-forth, which is common at Bisbee, as having close affinities with Spirifer anossofi, a Russian species which was then considered to be contemporaneous with the Middle Devon-ian index Stringocephalus in central Europe. Williams therefore believed the beds at Bisbee to be of Middle Devonian age. Ransome (1923) and Stoyanow (1936) reevaluated this assignment in the light of more recent interpretations of the Russian species and decided upon an Upper Devonian age for the Arizona brachiopod fauna. Ransome (1904, p. 33) used the name Martin Lime-stone for the Devonian beds of the Bisbee section. During the ensuing years, equivalent strata have been found to be widely distributed in the mountain ranges of south-central Arizona between the Mogollon Rim and the Mexican border. The Martin Formation is principally a carbonate sequence in the southern part of the state and maintains a relatively uniform thickness of the order of 375 feet in the various ranges where it is exposed. Toward central Arizona an increasingly high proportion of clastic material is admixed with the carbonate. The brachiopod fauna, on which Upper Devonian age assignment was based, is restricted to the upper part of the formation. Stoyanow (1936) reported the occurrence of Camarotoechia endlichi, a characteristic fossil of the Percha Formation of New Mexico and the Ouray beds of the Four Corners region, above the strata containing Theodossia hungerfordi and Cyrtospirifer whitneyi in Peppersauce Can-yon on the east side of the Santa Catalina Mountains nea