EXPLANATION OF PLATE 1. 



Fig. 1. Exposure of Middle Trias.sk' limestones on the south fork of American Canon, West 

 Humboldt Range, Nevada. Limestones extending from Saurian Hill (8) to the end of the ridge 

 beyond Fossil Hill (F). 



Fig. 2. Exposures of Upper Triassic, Hosselkus Limestone, on Brock Mountain, Shasta 

 County, California. The massive upper limestones are conspicuously pinnacled. The more 

 shaly beds of the lower horizon are less conspicuous, and are largely covered with thick brush. 



Fig. 3. Detail from fig. 2 showing the contorted shaly limestones of the lower hori/on from 

 their upper contact down almost to the Pit Shale. 



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