356 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



3,191.6 m.) above Hunga glacier, to the base of Billings Butte (see 

 pi. 108). For the estimated 2,100 feet (640 m.) of thin-bedded 

 limestone and shale above the Titkana, the name Lynx was proposed. 

 No attempt was made to collect fossils in this series, but the Lynx 

 was arbitrarily placed in the Upper Cambrian. (Fossils were found 

 in 1913 by me, and in 191 5 by Burling.) 



Immediately above the Lynx, thick layers made up of dark thin- 

 bedded limestones alternating with thin bands of grayish shale form 

 a banded cliff 300 feet (91.4 m.) or more high (Billings Butte, 

 pi. 94). The limestone layers are very fossiliferous, and as -the in- 

 cluded fauna was not typically Cambrian, it was referred to the Ordo- 

 vican in 1913. This dark band appears to form a cliff over which 

 Hunga glacier flows, and which then slopes up to form the upper band 

 of lyatunga Mountain (pi. 105). This is very noticeable from Tit- 

 kana Peak. This same dark band apparently extends across, although 

 interrupted by the Helmet faults, into Robson Peak about halfway 

 up between Berg Lake and the summit of the peak. As the Robson 

 Peak rises 7,592 feet (2,314 m.) above Berg Lake (Wheeler map, 

 1925), I assumed that there was at least 3,000 feet (914.4 m.) between 

 the Billings Butte fossiliferous beds and the summit of the peak. To 

 these limestones the name Robson was given. 



A preliminary study of the fossils collected from Billings Butte led 

 to the faunule being placed in the Ordovician, despite the Upper 

 Cambrian aspect of a number of the species. We now know that this 

 same fauna extends from Robson Peak south as far as central 

 Nevada, and that it is typical of a post-Cambrian, pre-Ordovician 

 formation that has been named the Mons in the Cordilleran Trough 

 of Alberta and British Columbia and referred to the Ozarkian. 



Recently this lower part of the Robson series has been separated 

 as the Chushina formation,* the upper 500 ? feet (152.4 m.) retaining 

 the name of Robson (see pis. 97, 99). 



When I began the systematic study of the fauna of the Mons 

 formation I wrote to the Director of the Geological Survey of Canada 

 inquiring if the collections made by Burling were available for study, 

 as Burling had resigned from the Survey. Dr. E. M. Kindle replied 

 that the collections were largely in the boxes as they were packed and 

 shipped from the field. The boxes were sent on to the United States 

 National Museum to Dr. Charles E. Resser. He found numbered 

 field labels indicating that the numbers were entered in Burling's field 

 notebooks. These were asked for and received and the laborious work 



^ Smithsonian Misc. Coll., vol. 67, no. 8, 1923, p. 458. 



