PRE-CAMBRIAN LITERATURE OF NORTH AMERICA 181 
to the action of bacteria and algae. Bacterial remains have not 
been identified in pre-Cambrian rocks, but numerous concretionary 
forms have been found in the Newland limestone of the Belt series. 
These forms are similar to the calcareous bodies formed by modern 
blue-green algae in fresh-water lakes. Chains of silicified cells 
which resemble the cell chains of modern blue-green algae were 
alsofound. ‘The similarities of structure between the pre-Cambrian 
and modern algoid forms are clearly demonstrated by a series of 
plates. Eight Algonkian algal forms are described by Walcott as 
occurring in the Newland limestone. The Greyson shale over- 
lying the Newland limestone has numerous crustacean remains— 
Beltina danai and many annelid trails representing five species. 
The next overlying formation of the Belt series, the Spokane shales, 
is credited with one species of algae. 
Walcott! briefly describes bacteria which he discovered in the 
Newland limestone, a formation of the Beltian series of Montana. 
The pre-Cambrian rocks? of the Dillon quadrangle include the 
Belt series, 3,000 feet thick, which are composed of slates, thin- 
bedded quartzite, and schists. They are unconformably above a 
series of schists and gneisses interbedded with limestones 5,000 feet 
thick which are correlated with the Cherry Creek group. 
VII. THE CORDILLERA OF CANADA 
Notable advances have been made in the study of the pre- 
Cambrian of the southern portion of the Rocky Mountain section 
by Daly, Schofield, and others. The pre-Cambrian in this section 
consists of two units, an older complex of clastic and chemical 
sediments, the Priest River terrane, Shuswap series, etc., folded 
and metamorphosed, and intruded by granites. The stratigraphic 
“separation of this older unit has not been fully accomplished. 
Unconformably overlying the basal rocks is a thick series of feebly 
metamorphosed clastic sediments and limestones, the Belt series, 
having characteristics of terrestrial sediments. They are coarsest 
and most fragmental in the western part of the section where they 
*C. D. Walcett, ‘Discovery of Algonkian Bacteria,” Nat. Acad. Sci. (1915), 
PP. 256-57, 3 figs. whet 
2A. N. Winchell, ‘Mining Districts of the Dillon Quadrangle, Montana and 
Adjacent Areas,” U.S. Geol. Surv. Bull. No. 574 (1914), 191 pp., 8 pls., 16 figs. 
