126 
MUSEUM BULLETIN NO. 2. 
So far as the writer is aware there are only three reported 
occurrences of the genus Crepicephalus in the beds below or 
immediately above the line separating the Lower from the 
Middle Cambrian. First in the Pioche formation of Nevada 
(page 120), second in a limestone with Albertella on Mount 
Stephen, British Columbia 1 , and third in interbedded limestones 
in a Middle Cambrian shale immediately overlying a quartzite 
on an island east of Niang-Niang-Kung, Liau-tung, Manchuria. 2 
The limits of this paper will hardly permit the inclusion of any 
further reference to the latter occurrence or to the relations 
between this shale series and the horizons under discussion. 
The Middle Cambrian aspect of the fauna of No. 5 of the Burton 
formation (page 125) was evident at the time its study was 
undertaken, but the association in the same 1-inch layer of 
two species of Crepicephalus and a representative of the genus 
Albertella suggested the comparison of the Burton formation 
with the Albertella fauna and the Pioche formation, horizons 
which had both been referred to the Lower Cambrian. 
Analysis of the Albertella fauna in the other regions from 
which it has been identified (see pages 118-119) revealed the lack 
of any necessity for the assumption that its Lower Cambrian 
age was infallible, and the writer turned his attention to the 
Pioche. This was shown (pages 121-123) to be divisible into 
Lower and Middle Cambrian zones respectively, and even to 
comprise faunas which, at the type locality of the Albertella 
fauna, are separated by 1,600 feet of limestone. At the type 
locality of the Pioche formation the range of faunas included 
in that unit does not appear to be so large and the Middle 
Cambrian horizon, to which the name Crepicephalus zone has been 
applied (see page 123) is to be correlated, at least tentatively, with 
the Burton formation. The correlation of the Burton formation 
with the Albertella fauna is based largely upon the presence in the 
former of an Albertella, a genus which, according to our present 
information, is confined in the Cordilleran region to this one 
horizon. The weight of evidence so largely opposes the Lower 
Cambrian age of these formations and corroborates their refer- 
’Walcott: Smithsonian Misc. Coll., vol. 53, No. 5, 1908, p. 213. 
2 Walcott: Research in China, vol. 3, 1913, p. 26, locality 35r. 
