WALOOTT.] IDAHO. 161 



IDAHO. 



In a letter to Prof J. D. Dana, dated Fort Hall, Idaho, July. 7, 1872, 

 Prof. F. H. Bradley wrote to announce the discovery of the Quebec 

 group. In a limestone he found many trilobites, some gasteropods and 

 brachiopods, and beneath the limestone a compact ferruginous quartz- 

 ite, which from its position he considered as representing the Potsdam 

 sandstone. 1 Near Malade City he discovered a series of limestones con- 

 taining Conocoryphe, Bathyurus, Dikelocephalus, Agnostus, etc. He 

 states in a later report that — 



The first examination of these Malade rocks was made at a point where the section 

 terminated below in a very quartzitic sandstone, which occupied the relative posi- 

 tion of the Potsdam, and was accordingly referred with doubt to that group in a let- 

 ter extract which was published in the August number of the American Journal of 

 Science. Later examinations have shown that this was really a part of the true 

 Quebec, whose base is not here exposed. 2 



The fossils collected by Prof. Bradley were studied by Mr. F. B. 

 Meek, who identified the genera Agnostus, Conocoryphe, etc., along 

 with several genera of the Lower Silurian fauna, and gave Prof. Bradley 

 the paleontologic data for his correlation. 3 



It is to be borne in mind that at the time of the work referred to, the 

 Quebec group was made to cover the horizons of the Potsdam, Caicif- 

 erous, and Chazy of the New York section. Again, throughout the 

 writings of Messrs. Hayden, Bradley, and Meek there are found many 

 references to the Quebec group, of strata that belong to different forma- 

 tions. This confusion arose primarily from the misinterpretation of the 

 mode of occurrence of the Upper Cambrian and Lower Silurian faunas 

 at Point Levis, Canada, the typical locality of the Quebec group. 



The Cambrian rocks north of Malade City were studied by Dr. A. C. 

 Pcale in 1877, in the Portneuf and Bannock ranges. He also visited 

 the Bear River range. Several carefully measured sections are pub- 

 lished with a summary of the rocks referred to the Silurian that will 

 be referred to in the description of the rocks of Idaho. 4 



The northern end of the Portneuf range, in the vicinity of Mount Put- 

 nam, came within the Teton district of Prof. Orestes St. John. The 

 central portion of the mountain is formed of ancient quartzite, alter- 

 nating with slaty micaceous shale, which alternates with limestones 

 above ; and on the northern terminus of Mount Putnam there is an 

 exhibition of the full series of the Paleozoic formations as developed in 

 this region. 5 



1 On the discovery of the Quebec formation in Idaho. Am. Jour. Sci., 3d sex., vol. 4, 1872, p. 133. 

 ' Bradley, Frank H. : Report of Frank H. Bradley, geologist of the Snake River division. U. S. Geol. 

 Snrv.of the Terr., 6th Ann. Rep., 1873, p. 201. 



3 Preliminary paleontological report, * * * with remarks on th% ages of the rocks, etc. TJ. S. 

 Geol. Snrv. of the Territories, embracing portions of Montana, Idaho, Wyoming, and Utah. 6th Ann. 

 Rep., 1873, pp. 431, 432. 



4 Report on the geology of the Green River district. U. S. Geol. Snrv. of the Terr., 11th Ann. Rep. f 

 1879, pp. 567-572, 599, 613-616. 



6 Report of the geological field work of the Teton division. U. S. Geol. Snrv. of the Terr. , 11th 

 Ann. Rep.. 1879, pp. 477-484. 



Bull. 81 11 



