GEOLOGIC FORMATIONS , 737 



tude of 13,068 feet, there is room for some 6,000 feet of beds (the strata 

 are very nearly horizontal) between the fossil horizon secured and the 

 top of the mountain. Now, the fossil horizon secured is equivalent to 

 the base of bed number 11 in the Titkana limestones, 1,100 feet below 

 the top of the formation, which, with the thickness of the Lynx lime- 

 stones (4,950 feet),- yields a total thickness of 6,050 feet between the 

 7,100-foot (elevation)" fossil horizon and the Extinguisher fauna. The 

 stratigraphic position of this fauna (Extinguisher) and the top of the 

 mountain should, therefore, coincide, and from this point of view there 

 seems to be no room in the top of Mount Robson for strata younger than 

 those carrying the Extinguisher fauna. 



(§ 23e.) The unbroken section of 9,809 feet, stretching from the sum- 

 mit of Mount Eobson (13,068 feet) down to the level of Lake Kinney 

 (3,259 feet), which lies close to the top of the basal elastics, also yields 

 a figure which compares very favorably with the 9,850 feet of measured 

 beds between the basal elastics and the Extinguisher fauna. Of course, 

 50 feet in 10,000 is more accurate than the rocks are, to say nothing of 

 the measuring, and we do not know the extent of the break in the Lynx 

 Mountain section or just how far below the surface oi Lake Kinney the 

 basal elastics begin; but while the closeness of the correspondence is 

 purely adventitious, the approximation confirms our interpretation of 

 the stratigraphy. 



(§23/.) Above the Lynx limestones there is a thin-bedded series of 

 shales and interformational conglomerates (375 feet exposed) carrying 

 an abundance of Ordovician fossils (the Extinguisher fauna) ; and while 

 these have nothing in common with the published descriptions of the 

 "Robson limestones,'^ except possible occurrence on the top of Mount 

 Robson, they might, perhaps, receive the name Robson shales at the hands 

 of a future student who shall find them there. They do occur in the 

 Extinguisher and in the summit of Mount Rearguard. 



LYNX FORMATION (§ 24) 



(§ 24a.) The Lynx limestones are described by Walcott as unfossilif- 

 erous and as beginning on the south slope of Titkana Peak, near Snow- 

 bird Pass, and extending over "Phillips Mountain" (Lynx Mountain) 

 into the base of "Billings Butte'' (the Extinguisher), to the horizon of 

 the Extinguisher fauna, with a thickness of 2,100 feet. 



(§ 246.) As determined by sections measured back of the summit of 

 Titkana Peak, in Lynx Mountain (Walcott's "Phillips"), and in Mount 

 Rearguard (Walcott's "lyatunga") (§§17 and 18), the Lynx formation 

 has a thickness of 4,950 feet to the horizon of the Extinguisher fauna, is 



