Field and laboratory studies have shown that the older type Cambrian sections in Nevada, Utah, and Wyoming are not usable for correlation, and that published faunal lists are incomplete and partly erroneous. In 1936 and 1937, fossils were accurately zoned in seven remeasured sections: Pentagon, Prairie Reef, and Scapegoat, Montana; Wind River Canyon, Wyoming; Blacksmith Fork and House Range, Utah; and Highland Range, Nevada.
The terms DuNoir and Gallatin are not applicable to the Wind River Canyon section which is now divided into the Depass (Albertan) and Boysen (Croixan) formations. The St. Charles (Croixan) formation in the original Blacksmith Fork section is redefined, as the upper 827 feet contain Ordovician fossils. The name Tatow limestone is applied to the youngest Waucobian rocks in the House Range. The upper 370 feet of the original Pioche shale in the Highland Range contains Albertan species and is named the Comet shale, the name Pioche being retained for the 600 feet of Waucobian rocks underlying the Comet and resting upon the Prospect Mountain formation. Few Middle Cambrian formations south of Montana can be correlated on evidence from fossils, other than the basal Ute with the Chisholm and Gordon, the upper Howell with the Damnation, and, doubtfully, the Wheeler and Marjum with the Pentagon. The Kochaspis upis fauna in the Steamboat limestone of Montana seems to be younger than the Marjumia-Neolenus fauna in the upper part of the Marjum limestone in the House Range.