EARLY CAMBRIAN STRATIGRAPHY. 
117 
Cambrian sedimentation in the Mount Bosworth and Mount 
Robson regions of British Columbia, see pages 105-110, relates to 
the occurrence of this fauna. In neither of these sections is the 
Albertella fauna found below Olenellus, and as has been outlined 
on the pages just referred to the occurrence of the latter genus 
above an Albertella in the Mount Stephen section seems to argue 
rather for the recurrence in the basal Middle Cambrian of a 
surviving member of the Mesonacidse than for the Lower 
Cambrian age of a fauna so distinct from its predecessors as the 
one in question. 
The collections from China which have so recently been 
described 1 contain a representative of the genus Albertella , to 
which the specific name pacifica has been applied. 2 It is 
to be distinguished from the species of Albertella described 
for the Cordilleran region by the presence upon its poster- 
ior margin of four instead of two spines, but it is referred to 
the genus without hesitation by Mr. Walcott. It occurs 
1,000 feet above a white quartzite in a low bluff on the shore 
of Tschang-hsing-tau island, in Liau-tung, Manchuria, and 
is the highest horizon from which fossils were obtained. Its 
resemblance to Albertella and its reference to a position well 
up in the Middle Cambrian appear to warrant its inclusion in 
the present discussion. 
The field relations of the horizon of the Albertella fauna may 
be summarized as follows: (a) In the Dearborn River section 
of Montana and at Elko, British Columbia, it is without close 
relations to known faunal horizons and occurs in a shale series 
conformably overlying a basal sandstone; ( b ) on Mount Bos- 
worth it was found in the drift but was referred to the Lower 
Cambrian because of the presence in a section 8 miles away 
(Mount Stephen) of Olenellus fragments both above and below 
its correlated horizon, a siliceous shale interbedded in a grada- 
tional sandstone, shale, and limestone series; (c) in the Mount 
Robson region it occurs in the section 350 feet down in a 900 
foot formation described 3 as composed of “bluish grey thin 
1 Walcott: Research in China, vol. 3, 1913, pp. 1-276. 
2 Idem, p. 106, pi. 12, fig. 3. 
Walcott: Smithsonian Mise. Coll., vol. 57, No. 12, 1913, p. 338. 
