KAWSOH MOUNTAINS. 771 



They are also found in coarse, gritty rocks overlying the main infusorial 

 strata, and occur more or less abundantly all the way up to the limestone. 

 None, however, have as yet been observed in the thick mass of gray acidic 

 tufas above the limestone, but have again been recognized in a series of 

 overlying cream-colored beds. In a stratum of compact grayish-lavender 

 sands, carrying some feldspathic material, Mr. Charles E. Wright has recog- 

 nized a number of forms described by Ehrenberg: 



GalUonella f 

 Spongolithis acicularis. 

 Pinnularia incequalis. 

 Cascidoniscus radiatus. 



Around the west end of the Montezuma Range, and through Caspar's 

 Pass, the relations of the eruptive rocks with the sedimentary strata are 

 obscured by the prevalence of Quaternary debris. At White Plains, how- 

 ever, it is clear that the pearlitic rhyohtes actually break through them, 

 and the basalts in the same region are later than the pearlites. The basalts 

 of the Kawsoh Mountains are all subsequent to the upturning and erosion 

 of the Tertiary, so that the period of deposition, probably carried back to 

 the Miocene by the organic remains of Fossil Hill, is certainly placed an- 

 terior to the ejections of rhyolites and basalts. The palagonite beds, which 

 form the lowest exposure of the sedimentary series in this part of the coun- 

 try, require for their formation an augite-bearing eruption, and, as the augitic 

 trachytes are an exceptional occurrence, and those of the Truckee Canon 

 are also later than the greater part of the rhyolites, it would seem necessary 

 to refer these Tertiary palagonites to a period at least as early as that of 

 the augite-andesites. 



Among the gray tufas which overlie the infusorial silica are some beds 

 of purely clastic sands, and one stratum of hard white crypto-crystalline 

 quartzite, which presents a botryoidal appearance on the upper surface, the 

 rounded protrusions being 5 or 6 inches in diameter. This seems to be a 

 true stratum, and may very likely have been a siliceous product of a hot 

 spring. 



So far as observed, there is only one body of pre-Tertiary crystalline 



