Geological Survey of California. 261 
formation extends from Mexico to British Columbia, occupying a vast 
area, although much broken up, interrupted, and covered by voleanic and 
eruptive rocks, and usually highly metamorphosed. 
Among the specimens from the Humboldt and Plumas county, Mr. 
Gabb recognizes at least four species as identical with European, while the 
whole facies of the collection is most strikin ly like that of the Hallstadt 
h Halobia, Monotis, Avicula, Pecten, 
a a Monoiis being the most widely diffused and the most abundant 
all. 
Accompanying this Triassic formation in the Sierra Nevada; and prob- 
E ugh, iaceien have been found to justify 
mentary portion of the great metalliferous belt of the Pacific coast of 
‘orth America is chiefly made up of rocks of Jurassic and Triassic age, 
With a comparatively small development of Carboniferous limestone, and 
that these two formations are so folded together, broken up, and meta- 
Morphosed in the great chain of the Sierra Nevada, that it will be an 
immense labor, if indeed possible at all, to unravel its detailed structure. 
While we are fully justified in saying that @ large portion of the auri- 
r of t of metam I jassic and Jurassic 
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to the west of the 116th meridian. On the other hand, we are able to 
State, referring to the theory of the occurrence of gold being chiefly lim- 
ited to Silurian rocks, that this metal occurs in no inconsiderable quantity 
12 Metamorphic rocks belonging as high up in the series as the Cretaceous. 
Allusion has already been made to the wide-spread occurrence in Cali- 
fornia of the Cretaceous formation. The coast-ranges of California and 
Oregon, indeed, are to a large extent made up of rocks of this age, 
thi al ps 
(Div.B). This latter should probably, judging from its stratigraphical po- 
Sition, correspond. with the For Hill group, or No. 5 of Meek and Hayden ; 
