WALcoTT] PALEONTOLOGY — DAKOTA. 233 



WESTERN BORDER OR ROCKY MOUNTAIN SUBPROVINCE. 



Iii a letter from Messrs. Meek and Hayden to Lieut. G. K. Warren, 

 dated February 8, 1858, attention is called to the identification of fos- 

 sils from a sandstone in the Black Hills equivalent to the Potsdam sand- 

 stone of the New York series. They recognized Lingula, Obolus?, and 

 fragments of trilobites, belonging to species known to occur in the 

 Potsdam formation in Wisconsin and Minnesota. 1 This notice was fol- 

 lowed in 1861 by the publication of the fir^t description of the Cambrian 

 fauna of the Rocky Mountains. The new species described but not 

 illustrated include Obolella nana, TJieca (Pugiunculus) gregaria, and 

 Arionellus (Crepicephalus) oiceni. 2 The descriptions of the species were 

 republished in 1802, in the American Journal of Science, in connection 

 with figures illustrating them. The last species is described as Ario- 

 nellus f oiceni. There were also identified from the same horizon Lingula 

 prima Conrad and Lingula antiqua Hall. 3 



The Black Hills fauna was again described by Messrs. Meek and 

 [I ay den in 1864, in their account of the paleontology of the Upper Mis- 

 souri. Lingula antiqua, mentioned in their letter of 1858, is identified as 

 Lingulepis pinnaformis Owen (p. 2), and the name L. dakotensis proposed 

 in the event of the shell being subsequently determined to be a new 

 species (p. 3). A description and illustration is also given of Lingulepis 

 prima Conrad (p. 3), Obolella nana. M. & H. (p. 4), Theca gregaria, M. 

 <& U. (p. 5), Agraulos oiceni, M. & H. (p. 9), (Arionellus (Crepicephalus) 

 oiceni, of the paper of 1861), and an undetermined species of Agraulos 

 (p. 10). All of the species are referred to the Potsdam or Primordial 

 sandstone. 4 



In 1876, when reporting upon the fossils collected by Captain Lud- 

 low's expedition to the Yellowstone National Park, Prof. It. P. Whit- 

 field described two species that are now referred to the Upper Cambrian 

 zone, Crepicephalus (Loganellus) montanensis and Arionellus tripunc- 

 iatus, referring them to the limestone of the Potsdam group overlying 

 the quartzite near Camp Baker. 5 



A preliminary report on the paleontology of the Black Hills by Prof. 

 R. P. Whitfield contains a description of Palceochorda prima, Palasophy- 

 cus occidentalism Lingulepis cuneolus, Ij. perattenuatus Crepicephalus (Lo- 

 ganellus) centralis, and C. (L.) planus. All of these species are referred 



1 Fossils of Nebraska. Letter from F. B. Meek an! F. V. Hayden. Am. Jour. Sci.,2d ser., vol.25, 

 1858, p. 439. 



^Descriptions of new Lower Silurian (Primordial), Jurassic, Cretaceous, and Tertiary fossils, col- 

 lected in Nebraska, witb some remarks on the rocks from which they were obtained. Phil. Acad. Sci., 

 Proc , vol. 13, 18UI, pp. 435, 436. 



3 The Primordial Sandstone of the Rocky Mountains in the Northwestern Territories of the United 

 States. Am. Jour. Sci., 2d ser., yol. 33, 1862, pp. 73, 74. 



4 Paleontology of the Upper Missouri ; a report upon collections made principally by the expeditions 

 under command of Lieut. G. K. Warren in 1855-'56. Invertebrates. Smithsonian Contributions No. 

 172, 1881, pp. 1-10. 



5 Descriptions of new species of fossils. Report of a reconnaissance from Carroll, Montana Terr., 

 on the Upper Missouri, to the Yellowstone Park and return, made in the summer of 1875 by Wm. 

 Ludlow, 1876, p. 141. 



