568 



PROCEEDINGS OF THE ALBUQUERQUE MEETING 



past summer I had occasion to extend my examination of tlie Ordovician of 

 tlie Black Hills in South Dakota, and at one locality 15 miles northwest of 

 Rapid I discovered fish remains similar to those previously reported from the 

 Bighorn mountains and hy JNIr Walcott' in tlie region west of Canyon City, 

 Colorado. The remains were submitted to Mr Waleott, and now await his 

 report as to genera and species. Unfortunately it was practicable to obtain 

 only a small mass of the fossil-bearing rock, but its stratigraphic position was 

 evident. The precise locality was one mile north-northeast of Nemo post office, 

 a small settlement on a branch railroad about half way between Deadwood and 

 Rapid. It is on the northeastern slope of the general Black Hills uplift, where 

 the rocks dip to the northeast at a low angle. 



The Ordovician in the Black hills is represented by a formation which has 

 been designated the Whitewood limestone from typical exposures on White- 

 wood creek about 2 miles below Deadwood. The rock is hard, massive, some- 

 what siliceous, and ordinarily of buff color with brownish spots or mottlings. 

 It contains large endoceras, maclureas, and corals of Trenton age. Its thick- 

 ness is 80 feet near Deadwood, but it thins rapidly to the south, and it is en- 

 tirely absent in the latitude of Rapid. The location of th.e southern margin 

 was not ascertained precisely, owing to talus which covers the slopes, but the 

 limit of the main outcrop is several miles north of Nemo. The limestone lies 

 iinconformably on Deadwood formation (Middle Cambrian), and is overlain 

 by the Englewood limestone of the Mississippian division of the Carboniferous. 

 Above and below it are thin bodies of green shales which yield no fossils, but 

 are included in the overlying and underlying formations. The lower shale, 

 and possibly also the upper one, extends south beyond the margin of the White- 

 wood limestone, usually constituting a slope between a bench of the upper 

 sandstone of the Deadwood and a cliff of the lowest limestone of the Carbon- 

 iferous. It was on a slope of this character, northeast of Nemo, that I ob- 

 tained the limestone fragment containing the fish remains. It probably repre- 

 sents a very thin oiitlier of the Whitewood limestone lying on the green shale 

 which here is regarded as the top member of the Deadwood formation. 



The next joaper read was 



TOPAZ-BEARING BHYOLITB OF THE THOMAS RANGE, UTAH 

 BY HOEACE B. PATTON 



The paper has been published as pages 177-193 of this volume. 

 The paper was discussed by 6. K. Gilbert. 



The next two papers were read without break. 



STRATA CONTAINING THE JURASSIC FLORA OF OREGON 

 BY J. S. DILLEB 



LOCAL SILICIFICATION OF THE KNOXVILLE 

 BY J. S. DILLEB 



2 Bulletin of tbe Geological Society of America, vol. 3, pp. 153-167 



