KUVOLITK «)F MACOdANY HILLS. 137 



( )n the west spm- dl' ('onihs Peak, in l)e(ls dippiiiji- to tlii' northeast, 

 occurs a belt ot" calcareous sliales about 150 feet iu width, carrying a rich 

 and varied taiuia (juitci siinihir to the fossil-bearing shale belts of Atr\|)a 

 and Brush ])eaks and with a nearly identical fauna. On page 7(> will be 

 found a list of the Combs Peak fauna, together with those of the other 

 peaks, showing the strong parallelism in the life from the tlu'cu! localities. 

 The precise locality from which this fauna was obtained is designated on 

 the map. All the ImmIs on tlie noi'th slope of (Joml)s i'eak l)elong to the 

 east side of the synclinal fold, dipping into the mountain and pas.sing 

 beneath the l)eils which form the summit. 



Browns Canyon, at the base of the motnitain, lies in the a.xis of an 

 anticlinal fold, the beds on the noith side dipping to the northeast at angles 

 seldom exceeding- 20°. At the head of this canyon, along the a.xis of the 

 fold, occurs a bo(h' of compact rhyolite, which has for the most part been 

 extravasated on the south side of a local line of faidting. It forms a hill 

 al)out 250 feet in height, whose outlines are sharply detined by drainage 

 channels wliich almost comph^tely surround it on all sides. The slopes of 

 the hill are strewn with lissile, sherdy fragments of rock characteristic 

 of tile entire mass. The rhyolite has a inicrocrystalliiie groundmass, with 

 but few mici-oscopic cr\stals of gray quartz, brilliant biotite Hakes, and 

 oc-casional dull orthoclases. In the middle f)f this rhyolite is an irregular 

 exposure of Nevada limestone about 100 feet in thickness, indicating that 

 the greater part of the lava is only a thin ifow over underlying limestones. 

 It is the single instance of a rhyolite ex|)osure observed in Mahogany Hills 

 east of Yahoo Canyon. 



Temple Peak.— From this rhyolite body the limestone hills rise gradually 

 to the northeast in gcmtle. Hat topped spurs, culminating in Temple Peak 

 (8,3MS feet), the highest j)oint l)etween Browns and Deiiio canyons. 

 Across this limestone body, from Browns Canyon to Dry Lake, the strata 

 dip persistently to the northeast, with a northwest anil southeast strike. 

 The limestones at the summit lie inclined at angles seldom exceeding 5°, 

 but are distinctly Ix'dded, and in physical habit and sequence of strata 

 resemble those about mid\va\' in the Ne\-ada limestone ejioch. Thc^ same 



