Field studies since 1931 have shown that: published type sections in Alberta and British Columbia were not usable for accurate correlation; genera restricted to widely separated stratigraphic horizons were lumped together in published faunal lists; formations, as defined, were not mappable units; and the Middle-Lower Cambrian boundary was incorrectly located.

Three sections were remeasured in 1938: Castle Mountain and Ptarmigan Peak in Alberta, and Ross Lake in British Columbia. The results are:

Emended definitions are given of the Lower Cambrian Fort Mountain, St. Piran, and Mount Whyte formations, and of the Middle Cambrian Ptarmigan, Cathedral, and Eldon formations. Fossils are zoned in each section, and revised faunal lists are given for each formation in which fossils were found. The Lake Louise shale is placed as a member of the Fort Mountain sandstone.

The new basal Upper Cambrian Pika formation is defined. Discovery of a pre-Cedaria fauna in these rocks lowers the Upper-Middle Cambrian boundary and furnished more precise evidence for its stratigraphic position.

The Mount Whyte formation of earlier writers is both Middle and Lower Cambrian in age. The upper 58 feet contains Kochaspis cf. cecinna and K. cf. gogensis and is lithologically identical with Ptarmigan limestone. Consequently, the Middle-Lower Cambrian boundary must be drawn just below the Kochaspis cecinna zone and between the emended Mount Whyte and Ptarmigan formations.

The Lower and Middle Cambrian formations are correlated tentatively with those in northwestern Montana, the House Range in Utah, and the Highland Range in Nevada.

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