REPORT OF THE CHIEF ASTRONOMER 115 



SESSIONAL PAPER No. 25a 



local erosion beforehand, for the Devonian limestone is represented in great 

 thickness only three or four rniles to the north. Many observations indicate 

 with some certainty that such orogenic movements in this part of the Cordilleran 

 region have not intervened between the deposition of the Jefferson limestone 

 and the upper Mississippian limestone. Some other than Willis' interpretation 

 of the Yakinikak contact seems legitimate, if not necessary. The writer knows 

 of no facts which involve any notable erosion unconformity between the 

 Devonian or Carboniferous sediments and the Cambrian-Beltian series of 

 southeastern British Columbia or of Montana northwest of the Belt mountains 

 and the Helena district. 



FOSSILS. 



The Devonian fossils were all found along the western edge of the eastern 

 block. The exact localities and the faunal lists prepared by Dr. H. M. Ami, 

 are here given. 



Station No. 1276.— At 114° 38' W. Long. ; seven miles west of the Flathead 

 river, and two miles and a half north of Boundary (6,400-foot contour) ; close 

 to great fault mapped. 



In a dark gray, impure, dislocated limestone, weathering peppery-gray, 

 yellowish-gray, or buff; fractured and recemented, more or less altered by 

 pressure. Surface marked by pitted structure in uniformly shallow rounded 

 depressions, or cavities, in which a layer of calcareous ( ?) matter appears, 

 as a thin lining on the inner wall. 



Age: Devonian. 



Formation: Jefferson limestone in the upper part of the Devonian system. 



Genera and species: 



1. Ohonetes (?) sp. An imperfectly preserved specimen not recogniz- 



able. Crushed valve showing punctate structure. 



2. Atrypa aspera. One specimen and two small fragments of this 



species characterize these limestones. 



3. Spirifer englemani. Exfoliated specimen in a block of limestone. 



Another individual, partially exfoliated, represents one of the 

 mucronate types of Spirifer englemani with a high hinge area, 

 and resembles very closely the Spirifer englemani from the 

 Jefferson limestone of Utah, Montana, and Nevada as repre- 

 sented in the collections of the U. S. Geological Survey obtained 

 by Dr. E. M. Kindle. 



Station No. 1277. — Eive hundred yards southeast of station No. 1276, and 

 close to great fault. 



The fossils occur in a dark, fractured and recemented limestone, weather- 

 ing peppery-gray; calcite veins prevalent. 



Age: Upper Devonian. 



Formation: Jefferson limestone. 



25a- — vol. ii — 84 



