EAST HUMBOLDT RANGE. 539 



S[)ur of limestone rising above the Quaternary of the valley. Upon the 

 foot-hills, directly back of Camp Halleck, the limestones again recur, and 

 here they wrap around a prominent mass of Archaean, curving into Sacred 

 Pass and skirting the crystalline rocks for a distance of 6 or 7 miles. There 

 is here no underlying quartzite, but the limestone rests directly on the 

 Archaean, and has yielded, near the point of contact, the following Coal- 

 Measure forms: 



Syringopora multattenuata. 



Productus costatus. 

 Athyris subtilita. 



The limestone is much shattered and decomposed. It is of a prevailing 

 light coter, is characterized by more or less earthy beds, and is doubtless a 

 much higher member than the black limestones directly north of the South 

 Fork. Further down the range, north of Sacred Pass, on the same spur, 

 there are obscure outcrops of limestone seen under the rhyolite, and for 

 the most part covered with glacial d(ibris. Observed dips gave 35° and 

 40° west. No fossils were found, but they probably represent a northern 

 extension of the Coal-Measure limestones already described. 



On the extreme northeast slope of the Archaean mass south of Wells 

 Station, on the Central Pacific Railraod, are a number of small isolated 

 patches of limestone resting upon the crystalline rocks in a manner similar 

 to those already mentioned on the western side of the range, and with the 

 same lithological habit. Imperfect forms of Coal-Measure fossils, too poor 

 for specific determination, were found imbedded in a light-gray rock, dipping 

 25° to the eastward. 



North of the limestone in Sacred Pass, and extending northward until 

 they rest against the Archaean body is a group of rhyolites, which are 

 chiefly a pale olive-green tufa, in' which are large crystals of vitreous 

 sanidin. East of Sacred Pass, the range is widened by the addition of an 

 outlying mass, which projects southward as a promontory surrounded by 

 the Quaternary of the valley. Between the promontory and the main 

 range in Clover Canon, the Archaean schists are broken through by a very 

 peculiar black rhyolite, having a brilliant resinous lustre, and resembling 

 externally many of the glassy andesites, except that it contains a very large 



