124 
MUSEUM BULLETIN. NO 2. 
is referred and with which the Pioche has been compared, 1 
yet in the Big Cottonwood Canyon and Oquirrh Range sections 
of Utah, the original collections appear to have mingled Pioche 
and Spence types (see page 121). Elsewhere, if we except 
the House range of Utah where the reference of a shale to 
the Pioche 2 is not based on fossil evidence, the two shales are 
not represented in the same section. Interesting, therefore, 
as the possibility of the suggested duplication may be, and the 
presence of Olenoides, Zacanthoides, and Orydocephalus (the 
latter particularly, see page 103) in the lower shale at Pioche 
tends still further to suggest its contemporaneity with the 
Spence, and, therefore, with the upper shale at Pioche, we 
must await the carrying out of detailed work upon these basal 
rocks in Nevada, contenting ourselves for the present with the 
suggested division of the lower shale (the Pioche) into two zones 
and the tentative correlation of the upper or Crepicephalus zone 
with the Albertella fauna and with that of the Burton formation. 
Under a system of nomenclature in which formations will 
be referable to and comparable with lithologic or stratigraphic 
units, the Pioche formation, from our present knowledge, 
appears to be an identifiable series of interbedded shales and 
limestones occupying a transitional zone between true quartzite 
and limestone series. The two faunas into which the Pioche 
of the Big Cottonwood section is divisible are, however, separated: 
(a) in the Bear River Range, 100 miles to the north, by several 
hundred feet of quartzites and limestones; ( b ) in the Mount 
Bosworth section by 1,600 feet of massive limestones and 350 
feet of thin-bedded limestone, sandstones, and shales carrying 
a new fauna ( Albertella ); (c) in the Mount Robson section 
by 4,350 feet of limestones and shales including the same new 
fauna ; ( d ) in the House range by 205 feet of limestones; 
(e) at Pioche, if the stratigraphy has been correctly solved, 
by 600 feet of limestone and the Crepicephalus zone of the 
Pioche formation, a horizon comparable with the Albertella 
fauna in the Mount Bosworth section; and (/) in the Highland 
range by 1,100(?) feet of limestones and shales. Such a con- 
l WaIcott : Smithsonian Misc. Coll., vol. 53, No. 5, 1908, p. 171. 
2 Idem, pp. 171 and 184. 
