844 FLORAL ZONES OF THE POTTSVILLE FORMATION. 



.su))ject of fraginontary descriptions ])y Taylor/ Rogers," and Suiith.^ 

 The cross section giveii by the first-named author is repeated in more 

 comph^teform hy Kogers and the second geological survey', though in 

 the pul)lications of the latter the boundary of the red shale appears to 

 have been drawn where it might theoretical!}' lie if the Buck Mountain 

 (Twin) coal were the lowest Lykens coal. The position and extent of 

 the drifting in the vicinity of this gap are shown in mine sheet xxiii. 

 From the section which I give in PL CLXXXVII, Fig. 2, it appears 

 that the Pitch l)ed, the next coal below Bill's V)ed, pro})ably lies within 

 the group of conglomeratic plates at the top of the Pottsville forma- 

 tion. The roof shales of the coal, which I interpret as the probable rep- 

 resentative of the Buck Mountain coal, furnish the following species: 



Marioj^teris marietta (Schloth.)Zeill. var. 



nervosa (Brongn.) Kidst. 

 Mariopteris ocfidentali;^ T>. W. 

 Pecopteri.s uiiita Brongn. 

 Pecopteri.s pusilla Lx.? 

 Alethopteris aquilina (Schloth.) Goepp. 



Neuropteris Desorii Lx. 

 Neuropteris ovata Hoffni. 

 Neuropteris vermieularis Lx. 

 Neuropteris fiml^riata Lx. 

 Neuropteris Scheuchzeri Hoffm. 

 Linopteris obliqua{Bunb.) Pot. 



The composition of this fiora indicates a horizon in the basal portion 

 of the Lower Coal ^Measures, or in the Allegheny series. A drift in 

 the same horizon on the west side of the gap 3'ields large numbers of 

 Aldltopterls Serlii (Brongn.) Goepp., Neurojjteris ScheuchzeriYLo^m.. ^ 

 and Aster(>j>hijll/frs equl><i4if<n'mi>< (Schloth.) Brongn. 



P>el<)w the Pitch l)ed there is but little, if any, evidence of search for 

 coals in the Pottsville formation at Rausch Gap. Here, as well as in 

 Gold ]\Iine and Black Spring gaps, effort was made to find the coals of 

 the Lorberry and Fishing Creek gap sections, which were seen to pass, 

 in the Dauphin Basin, to the north of the crest of Sharp Mountain 

 instead of to the south of the latter. In his discussion of the region 

 under consideration. Dr. Taylor,* whose reports and notes form the 

 basis of the later publications relating to the district, remarks that 

 " no examination for veins [coals] south of the backbone ledge of Sharp 

 Mountain has taken place herea])Outs.'' Owing to the except ionall}^ 

 favoiablc conditions at the southeast corner of the gap, the top of the 

 red shale was located by me, with a prol)ably high degree of certainty, 

 at about 1,175 feet l^elow Bill's coal, which I have assumed to be near 

 the horizon of the Buck Mountain bed. The boundary can be hardly 

 more than 75 feet higher. 



YELLOW SPRINGS GAP. 



(Station 'JS, Pi,. CLXXX.) 



At "^'('llow Spring.s, \\ miles west of Rausch Gap, there is a high gap 

 in the mountain, through which a .small stream, draining a section about 



1 Report on the Stony Creek Estate, Pt. II, p. 19, pi. 147, (ig. 4. 

 2Geol. Peiinsylviinia, Vol. II, Pt. I, p. 19.5. fig. 182. 

 •■'Summary Final Report. Vol. Ill, Pt. I, p. •.'11-1. 

 <0p. cit., p. 21). 



