TITLES AND ABSTRACTS OP PAPERS 97 



sand, ^ in which was found the famous Staddler well, which started our gas 

 boom. This well had an initial flow of over 12 million cubic feet daily. This 

 horizon was found about 2,400 feet below the surface. Three hundred feet 

 below this is the so-called Clinton sand, which has been the source of most of 

 our gas. I may also state, in the absence of Gushing and Ulrich, that for over 

 three years they have considered the Clinton sand as Medina age, thus agree- 

 ing with the conclusions just expressed by Doctor White. 



Eemarks were also made by Professors A. P. Coleman and J. F. Kemp, 

 and reply was made by the author. 



TENTATIVE CORRELATION OF THE PENNSYLVANIA STRATA IN THE EASTERN 

 INTERIOR, WESTERN INTERIOR, AND APPALACHIAN REGIONS BT THEIR 

 MARINE FAtlNAS 



BY T. E. SAVAGE 



{Al)stract) 



In this paper the faunas of the successive marine fossil-bearing horizons in 

 the western interior, eastern interior, and Appalachian regions are compared. 

 A study of the vertical range of the species of Pennsylvanian fossils in these 

 regions has shown that certain species have such limited vertical range that 

 it is thought they can be used as trustworthy markers of different horizons in 

 the respective basins, and that these furnish more accurate means of correla- 

 tion than any criteria that have hitherto been available. 



These studies indicate that the arch that at present separates the eastern 

 interior and western interior coal basins along the Mississippi River was de- 

 veloped at the close of the Mississippi an period, before the earliest Pennsyl- 

 vanian sediments were laid down, and that it effectively separated the seas 

 that occupied a large part of Illyiois and Missouri during Pennsylvanian time, 

 although toward the north these seas may have been temporarily united during 

 a small part of the PottsviUe epoch. 



Eead in fnll from manuscript. 



Remarks were made by Dr. J. M. Clarke. 



PRECAMBRIAN ROCKS IN THE MEDICINE BOW MOUNTAINS OF WYOMING 

 BY ELIOT BLACKWELDER AND H. F. CROOKS 



{Abstract) 



The Medicine Bow Range, west of Laramie, Wyoming, hitherto neglected by 

 geologists, contains one of the most varied sections of Precambrian rocks in 

 western United States. In addition to the usual gneissic and schistose com- 

 plex, more than 25,000 feet of slightly metamorphosed sedimentary rocks, such 

 as quartzites, slates, dolomites, lava flov/s, pyroclastics, and tillites, are ex- 

 posed without repetition. Although but little of the detailed study of the rocks 

 has yet been carried out, a preliminary outline can be given, and the empirical 

 sequence will be briefly discussed. The correct interpretation of the stratig- 

 raphy depends on an accurate knowledge of the structure, and that remains in 

 doubt. In this interesting case it has been found that the testimony of the 

 primary sedimentary structures is gerierally opposed to the apparent implica- 



