738 L. D. BURLIXG CAMBKO-ORDOVICIAX XEAR MOUNT ROBSON 



abundantly f ossilif erous, and is one of the most heterogeneous of the 

 formations in the region. 



(§24c.) The Lynx formation extends from the base of the Upper 

 Cambrian to the base of the Ordovician. It is marked at the base by a 

 series of shales which exhibit shallow-water phenomena (§ "), and, like 

 the Upper Cambrian in so much of the Cordillera, is frequently charac- 

 terized by interformational conglomerates. The limestones forming the 

 upper part of the Lynx formation are cliff-forming, and the line between 

 the Upper Cambrian and the Ordovician is drawn between them and an 

 overlying series of shales and thin interbedded interformational con- 

 glomerates which carries the Extinguisher fauna and which is referred 

 to the Ordovician. The line occurs about halfway up in the section ex- 

 posed in the Extinguisher and at the top of Mount Rearguard. 



(§24(7.) Walcott describes the Lynx formation as lying below the 

 Extinguisher fauna — a definition which is accepted — one of the reasons 

 for the discrepancy between the figures of 2,100 and 5,000 feet respec- 

 tively for the thickness of the formation being his assumption that Mount 

 Rearguard exj^osed the Middle Cambrian, and that the Extinguisher 

 beds directly overlay those of Mount Lynx. Mount Rearguard exposes 

 the upper portion of the Lynx and is itself directly overlain by the Ex- 

 tinguisher beds and faima. Mount Lynx exposes only the lower portion 

 of the Lynx formation. 



Titkaua limestones : Walcott, Smithsonian Miscellaneous Collections, volume 



■ 57, number 12, 1913, pages 330, 334, 337, and 341. 

 Hitka formation, as far as both position in section and exposure in Hitka 



Mountain : Walcott, idem, pages 334, 338, and 341. 

 Titkana : Burling. Museum Bulletin number 2, Geological Survey of Canada, 



1914, page 109. 

 Hitka : Burling, idem, page 109. 



Titkana : Walcott, Problems of American geology, New Haven, 1915, page 179. 

 Hitka : Walcott. idem, page 179. 



TITKAXA LIMESTOXES (§25) 



(§25a..) According to Walcott, the Titkana limestones have an esti- 

 mated thickness of 2,200 feet and are best seen in the west slopes of 

 Titkana Peak and in Mount Rearguard ("lyatunga"). As has already 

 been shown (§§18 and 24^), this formation is not present at all in 

 Mount Rearguard, but the section in Titkana Peak exposes both the top 

 and bottom of the formation. 



Two fossil horizons were secured by Walcott — one, locality 61?;, in a 

 cliff just above the Robson Glacier, and the other (61Z and 61m) 1^ 

 miles west-northwest of the summit of Titkana Peak. The first of these 



