i62 The American Geologist. March. I'joi. 
silver mines contain an abundance of cyathophylloid corals 
and are referred to the Carboniferous. The dark colored 
limestones of the Mule mountains, at Tombston;^,* and also 
those at the American mine in the Svvisshelms are similarly 
referred, and are doubtless a part of the extensive series of 
limestone and shaly beds of the northern portion of the Santa 
Ritas ; and a portion of the strata of the Whetstone range 
and of the Dragoons, and of the Galiuro mountains are of the 
C'arlioniferous age. 
Caiiibriaii. Most of the outcrops of massive quartzyte 
uplifted and in contact with granite at several distant places 
are referred with some hesitation to the Cambrian. Suc!i 
outcrops are found from western Sonora in nearly all the 
chief uplifts as far east as the Chiricahuas. In northern 
Sonora near the boundary line in nearly the southeastern con- 
tinuation of the Gila and Mohawk uplifts, a well defined 
ancient quartzyte stands in vertical beds alongside of an 
intrusive granite. This quartzyte is marked by perforations 
like those of the Potsdam and probably properly referable 
to S eolith us. Conglomerates and quartzytes occur in the 
lUiboquirasi range and in the Tucson mountains where there 
is a great thickness of strata in regular folds, probably rep- 
resenting a large part of the Palaeozoic. Massive conglom- 
erates with thoroughly rounded pebbles firmly cemented to- 
gether occur near the source of the Canada de Oro in the 
northern part of the Santa Catalina mountains ; also at the 
American Flag rancho in the same mountain range, ^^'e 
again find coarse conglomerate opposite the mouth of the 
Arirapa near the site of old Fort Grant where quartzytes 
also occur resting on granite. Thickly bedded conglomerates 
occur over wide areas south of Tucson in the region of 
Ariraca and again in the northern portion of the Chiricahuas. 
It is not at present possible to correlate all these occurrences 
which no doubt represent dififerent horizons, but they are all 
believed to be Palaeozoic, or older. They bear united tcsti 
mony to the former existence of shore-lines and rapid cur- 
rents. 
Beginning of Arizona Land. The Santa Catalina, Rin- 
* See my paper on the Geology and Vein.*! of Tombstone, Trans. Am. Itist. 
Min. Engrs., X, 334. 
