276 5. L. POWELL 



microscopic study. The fossils show a smooth, polished, black, 

 chitinous surface. Near the middle of the formation along with 

 the various species of graptolites there are many forms of Triarthrus 

 becki, and Leptoholus walcotti. 



In New York the formation — Normanskill — carrying the same 

 fossils is described by Ruedemann as a deep bluish-black, thick- 

 bedded argillite with conchoidal fracture, and iron-stained cleavage. 

 This description applies equally well to the Athens shale of Vir- 

 ginia. In Folio 16 U.S.G.S. Keith says of the Athens shale in 

 Tennessee: "It is everywhere composed of blue and black shales, 

 which do not vary in appearance. The black shales are found 

 at the bottom of the series and contain lingula and numerous grap- 

 tolites. The blue shales gradually replace the black shales in pass- 

 ing up through the series, and when fresh consist of thin light 

 blue, shaly limestones." It is evident that the blue shales above 

 the black, which he says consist of thin, light-blue, shaly lime- 

 stone, represent the Trenton in that section, and the black shales 

 below with the included graptolites and lingulae represent the 

 Athens. Keith, in that section, also represents the Athens shale 

 as immediately underlying the Tellico sandstone. Immediately 

 below the Athens shale he describes a limestone formation consist- 

 ing of massive blue and gray limestones, shaly and argillaceous 

 limestones, and marbles. These beds are all very fossiliferous, and 

 fragments of corals, crinoids, brachiopods, and gastropods are so 

 abundant as sometimes to make most of the bulk of the rock. The 

 upper beds of the formation consist of more or less coarsely crystal- 

 line marble. This is exactly the position of the marble beds in the 

 Black River formation, and anyone at all familiar with it will see 

 at once from the above description that the Athens shale of Tennes- 

 see, as well as that in Virginia, rests upon the Black River. 



The conglomerate R. Ruedemann described^ as occurring in the 

 Normanskill of New York, although looked for, was not observed. 

 Neither does the Rysedorph conglomerate occur here, which 

 Ruedemann describes as intercalated in undoubted Normanskill, 

 and containing in pebbles as well as matrix, as its youngest fossils, 

 those of lower Trenton aspect. There does occur here, however, 



^Bull.42,N.Y.S.M. 



