EARLY CAMBRIAN STRATIGRAPHY. 
99 
Cambrian. No Lower Cambrian fossils have been found in the 
Tonto, the lowest horizon represented being the lower portion 
of the Middle Cambrian. 
Utah, House Range. — No Lower Cambrian fossils, with the 
exception of annelid trails and trilobite ? tracks ( Cruziana ), have 
been found in the House range in western Utah, though that 
section is only 100 miles distant from Pioche, Nevada, where the 
Lower Cambrian Pioche formation is so typically developed. 
The base of the section is formed of a series of unfossiliferous 
quartzitic sandstones and arenaceous shales 1,500 or more feet 
in thickness, conformably overlain by arenaceous limestones of 
Middle Cambrian age. In view of the proximity to Pioche 
there appears to be no reason for doubting the reference of the 
quartzitic series to the Lower Cambrian, but the Pre-Cambrian 
appears to be unrepresented. The horizon of the Spence shale 
is well represented in the House range 200 feet above the quartz- 
itic series. 
Utah , Oquirrh Range. — The first reference to the Cambrian 
of the Oquirrh range is by Howell 1 who mentions Primordial 
“shale carrying several species of trilobites and Discina” and 
it is probable that this material furnished the species for which 
White 2 proposed the name Olenellus gilberti. Emmons 3 found a 
fauna in 100 feet of greenish yellow clay slates immediately 
overlying a quartzite series which is not listed as containing 
Olenellus and which is apparently referable to a higher horizon, 
the Bathyuriscus produdus zone (see page 101). Walcott 4 
mentions a shale in the Oquirrh range as carrying both of these 
faunas ( Olenellus gilberti and Bathyuriscus produdus ) but in 
1891 6 he credits the collection to the Wheeler (100th Meridian) 
Survey and states that it probably represents an artificial 
mixing of the collections from two distinct zones similar to that 
described for Big Cottonwood canyon (page 101) and Pioche 
(page 121). The shale near Ophir City in the Oquirrh range 
is thus apparently the lithologic, stratigraphic, and faunal equiv- 
alent of the Pioche shale in the Big Cottonwood Canyon section. 
1 U. S. Geog. Surveys West 100th Meridian, vol. Ill, 1875, pp. 237-238. 
2 Idem, vol. IV, 1877, pp. 45-4G. 
: U. S. Geol. Expl. 40th Parallel, vol. II, 1877, pp. 443-144. 
'Bull. U. S. Geol. Survey, No. 30, 1886, pp. 39-40, 
i Idem, No. 81, 1891, pp. 319—320. 
