

walcott.J SUMMARY — MONTANA. 325 



The fauna collected in the Gallatin River section by Dr. TIayden in 

 1872 was studied, by Mr. Meek, who recognized eighteen species. From 

 the lowest division he identified the genera Cruziana, Lingulepis, or 

 Lingula, Conocoryphe, Bathyurus, or Asaphus. From the third divi- 

 sion he described Bathyurus serratus, B.f haydeni, Conocoryphe (Con- 

 ocephalites) gallatinensis, Iphidea subtilis, and Agnostus bidens ; and iden- 

 tified a species of Conocoryphe, Hyollthes gregaria, and Acrotreta sub- 

 conica. From the second divisiou the genera Acrotreta and Lingula 

 are identified, and from the upper or first division Asaphus ?, Bathyu- 

 rus? Conocoryphe, and Lingulepis. 1 This fauna has the facies of 

 the Upper Cambrian zone, although that of the fourth or lowest di- 

 vision may prove to belong to the Middle Cambrian. As a whole the 

 Cambrian of the Gallatin region is formed of a sandstone at the base, 

 above which occur limestones carrying a fauna characteristic of the 

 upper portion of the group. 



The presence of the Upper Cambrian on the southwestern side of the 

 Little Belt Mountains and on the southern side of the Elk Eange was 

 proved by Messrs. Dana and Grinnell when they discovered fossils of 

 this age. The section near Camp Baker, southwest of the Little Belt 

 Mountains, is estimated as follows : 2 



Quartzite, 20 feet; variegated shales, mostly bright rod, also green and bine, 150 

 feet ; limestone in a double series of ledges, 80 feet ; quartzite, reddish, slightly mica- 

 ceous, then a series of colored slates, mostly green, followed by shales and thin beds 

 of sandstones and limestones, in all probability 1,500 feet ; still further conformable 

 shales, 1,000 feet. These extend toward the north farther than we could follow 

 them. It is enough to say that the total thickuess of the conformable strata under- 

 lying the fossil-bearing limestone can not be less than 3,000 feet, and is probably 

 much more. 



The same authors state that they identified similar rocks at Moss 

 Agate Springs, at the south extremity of the Elk Range of mountains. 

 The strata there are red shales, quartzites, and limestones like those at 

 Camp Baker, the limestones containing many fragments of trilobites. 

 The fossils collected were studied by Prof. R. P. Whitfield, who de- 

 scribed Crepicephalus (Loganellus) montanensis and Arionellus tripunc- 

 tatusf species that occur in the Upper Cambrian horizon, the former in 

 the Black Hills and Big Horn Range, and the latter in central Texas. 



From his observations at numerous points Dr. F. V. Hayden con. 

 eluded that the outcrop of the sandstone referred by him to the Pots- 

 dam extended entirely around the Big Horn Mountain Range. Near 

 the sources of Powder River he found a series of sandstones underlying 

 the Carboniferous limestone, resting unconformably upon the schistose 

 and clay slates of the A^oic series in very nearly the same manner as 



1 Preliminary paleontological report . . . with remarks on the ages of the rocks, etc. TJ. S. 

 Geol. Sui v. of the Terr., 6th Ann. Rep., 1873, pp. 463, 464. 



2 Geological report. Report of a geological reconnoissance 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. 133. 



s Descriptions of new species of fossils. Ibid. p. 141. 



