106 
MUSEUM BULLETIN NO. 2. 
recently been subdivided by Walcott 1 who places the boundary 
between the Bow River group and the overlying Castle Mountain 
group 2 below a 20-foot bed of interbedded arenaceous limestones 
and siliceous shales (the Olenellus canadensis zone) forming the 
base of the Mount Whyte formation. The correlation of the 
top of this bed with the upper boundary of the Bow River group 
would make that group synonymous with the Lower Cambrian, 
at least so far as their upper limits are concerned, and would 
permit the relegation to the Middle Cambrian of the upper 
portion of the Mount Whyte in spite of the inclusion within that 
horizon of fragments which appear to be referable to Olenellus. 
The correctness of this reference is indicated (a) by close faunal 
affinities between the underlying Bow River group and the 20- 
foot bed in question and (b) by the presence j ust above that hori- 
zon of the Albertella fauna (see pages 116-120 ), a striking assem- 
blage which is here known, in its typical expression, only from 
two drift blocks. One of these loose fragments weighing several 
tons has been thoroughly tooled by both Mr. Walcott and the 
writer without discovering the smallest fragment referable to 
Olenellus. The absence of this genus in strata so widespread 
(Montana and British Columbia, page 113) and so minutely 
studied, here possesses special significance since these layers 
appear to be interbedded between strata carrying Olenellus and 
supports the impression that the occasional appearance in the 
Mount Whyte of fragments referable to the latter genus is to 
be explained by the recurrence of a lingering type. 
The discussion of the basal Cambrian sedimentation in the 
Mount Robson district (see below) also contains additional 
notes on the Mount Bosworth section. 
British Columbia and Alberta, Yellowhead Pass Region, Mount 
Robson Section. — In 1901 McEvoy 3 described and mapped the 
geology in the vicinity of Yellowhead pass, dividing the basal 
stratigraphic succession into a “Lower Cambrian Bow River 
series” and an “Upper Cambrian Castle Mountain group” 
1 Walcott: Smithsonian Misc. Coll., vol. 53, No. 5, 1908, pp. 204-217. 
2 McConnell: Ann. Rept. Geol.and Nat. Hist. Survey Canada for 18S6, Part D, 
1887, pp. 24 D-29 D. 
3 Ann. Rept. Geol. Survey Canada for 1898, vol. XI, 1901, Part D, with map. 
