ON THE STOCKDALE SHALES. 707 



and those of the Gala group ; indeed, Prof. Lapworth has himseK 

 shown the relationship of these in his papers on " The Moffat 

 Series "* and " On the Geological Distribution of the Ehabdophora "t ; 

 but a most remarkable similarity between the Scotch and North of 

 England beds becomes apparent when we come to compare the zones 

 of each, for not only are the fossil contents of the zones of the two 

 areas remarkably similar, but a decided resemblance can be traced 

 when we compare the lithological characters. 



The Lower Skelgill Beds are flaggy beds like those of the zones of 

 Diplograptus acuminatus and Diplograptus vesiculosus at the base of 

 the Birkhill Shales. 



The Middle Skelgill Beds resemble the Monogra/ptus-gregarius 

 zone, not only in the blackness of the shales, but also in the develop- 

 ment of interstratified mudstones containing calcareous nodules. 



The Upper Skelgill Beds resemble the zones of Monograptus 

 sjainigerus and Rastrites maximus in that the beds are generally of a 

 lighter colour than those of the underlying zones. 



The Grits and pale Shales of the Browgill Beds are comparable 

 with similar rocks in the Gala group. 



Comparing the zones in detail : — 



1. The zone of Diplograptus acuminatus at the base of the Birk- 

 hill Shales is like the same zone at the base of the Skelgill Beds. 

 Both are slightly calcareous flaggy shales, and the two fossils found 

 in the acuminatus-zone at Browgill, viz. Diplograptus acuminatus, 

 Nich., and CIi7nacograptus normalis,IjSii^w.,hot]i occuv in the Birkhill 

 zone. The two other species found in the Birkhill zone, DimorpJio- 

 graptus elongatus^ Lapw., and Diplograptus vesiculosus, Nich., have 

 not yet turned up in the Lake-district ; but possibly a further search 

 will result in their discovery. 



2. The zone of Diplograptus vesiculosus, ISTich., is represented by 

 the zone of Dir^iorpliograptus confertus, Nich. In both areas the 

 beds consist of black flagstones. 



Of the fossils found in this zone in the Lake-district, Monograptus 

 tenuis, Portl., M. attenuatus, Hopk., Dimorpliograptus elongatus, 

 Lapw., Diplograptus vesiculosus, Nich., and Glimacograptus normalis, 

 Lapw., are also found in the corresponding Birkhill zone. 



Monograptus revolutus, Kurck, M. Sanclersoni, Lapw., 31. lepto- 

 theca, Lapw., Dimorpliograptus confertus, Nich., D. Swanstoni, Lapw., 

 and Diplograptus longissimus, Kurck, have not been recorded from 

 the Birkhill Shales, but they are mainly found on one horizon in the 

 Lake- district, and may eventually turn up in the Scotch area. 



3. The zone of Monograptus gregarius, Lapw., is undoubtedly 

 represented by the zones of Monograptus fimhriatus, M. argenteus 

 and M. convolutus, with their interstratified mudstones. In all these 

 zones Monogi^aptus gregarius is abundant, and it is practically limited 

 to them, only one specimen having been discovered in the CUngani- 

 band. 



Of the thirty-three species of Graptolites found in these zones in 



* Q. J. G. S. xxxiv. p. 337. 



t Ann. & Mag. Nat. Hist. ser. 5, vol. iii. p. 39. 



