



walcott.] DAKOTA. 215 



In notes explaining the second edition of a geological map of Ne- 

 braska and Kansas in 1858 Dr. F. V. Hayden 1 states that tbe existence 

 of the Potsdam sandstone on the eastern slope of the Rocky Mountains 

 was discovered during Lieut. G-. K. Warren's expedition to the Black 

 Hills in the summer of 1857. 



In March, 1858, Messrs. Meek and Hayden presented a paper to the 

 Academy of Natural Sciences, Philadelphia, containing "some remarks 

 on the geology of the Black Hills and portions of the surrounding coun- 

 try." In this a section of the formations is given, in which the u Pots- 

 dam" sandstone is given a thickness of 30 to 50 feet and is said to con- 

 tain Lingula, Obolus ?, and fragments of trilobites. 2 The sandstone is 

 described as of a reddish and grayish color, composed of angular grains 

 of quartz, cemented by siliceous and sometimes small portions of calca- 

 reous matter. The fossils then identified were Lingula antiqua Hall, great 

 numbers of a small shell similar to L. prima Conrad and fragments of 

 trilobites. 3 The information contained in this first paper by Messrs. Meek 

 and Hayden was also published in the American Journal of Science, 4 the 

 Canadian Naturalist (vol. 3, 1858, pp. 182-193), the report of the Chief 

 of Engineers to the Secretary of War, 1858, 5 the American Journal of 

 Science (vol. 25, 2d ser., p. 439,1858), the Proceedings of Philadelphia 

 Academy of Science (vol. 10, p. 139, 1859), and in a reprint of the Pre-, 

 li mi nary Report of the Exploration of Nebraska and Dakota, issued in 

 1875, which is the official account of Lieut. G. K. Warren's exploration 

 transmitted to the Chief of Engineers. 



In a paper on the Primordial sandstone of the Rocky Mountains and 

 Northwestern Territories of the United States Dr. Hayden describes 

 the sandstone he referred to the Potsdam in the Black Hills in con- 

 siderable detail, as follows : 6 



3. Variegated sandstone, of gray and ferruginous red color, composed chiefly 



of grains of quartz and particles of mica, cemented with calcareous matter. 

 Some portions of the bed are very hard, compact, siliceous; others a coarse 

 friable grit, others a conglomerate. Fossils: Lingulaprima, L. antiqua,) Obo- 

 lella nana, and fragments of a trilobite, Arionellus? oweni. . . 50 to 80 f. 



4. Stratified azoic rocks standing in a vertical position for the most part. 



.The " Potsdam" sandstone is again described by Dr. Hayden in 

 1863, 7 and in the following year he published, in connection with Mr. 



1 Explorations under the War Department; explanations of a second edition of a geological map of 

 Nebraska and Kansas, based upon information obtained in an expedition to the Black Hills under 

 command of Lieut. G. K. Warren. Am. Jour. Sci.. 2d ser., vol. 26, 1858, pp. 276-278. 



2 [Some remarks on tbe geology of the Black Hills and portions of tbe surrounding country.] PbiL 

 Acad. Sci., Proc, vol. 10, 1859, p. 44. 



3 Op. cit.,p.49. 



4 Explorations under the War Department; explanations of a second edition of a geological map of 

 Nebraska and Kansas, based upon information obtained in an expedition to tbe Black Hills under 

 command of Lieut. G-. K. Warren, Top. Engr., U. S. A. Am. Jour. Sci., 2d ser., vol. 26, 1858, p. 276. 



6 Catalogue of tbe collections in geology and natural history obtained by the expedition under com- 

 mand of Lieut. G-. K. Warren. Appendix to Kept. Sec. of War in Itept. of Topog. Eng. for 1858. (Re- 

 print edition of 1875, pp. 59-125. Map.) 



6 Tbe Primordial sandstone of tbe Rocky Mountains in the Nortb western Territories of the United 

 States. Am. Jour. Sci., 2d ser., vol. 33, 1362, p. 70. 



7 On the geology and natural history of the Upper Missouri. Am. Phil. Soc. Trans., vol. 12, new 

 ser., 1863, pp. 36-38. 



