307 

 THE CORRELATION OF THE VOREDALE AND 

 PENDLESIDE SERIES. 



VVHEELTON HIND, M.U., F.R.C.S., F.G.S. 



Mr Cosmo Johns' paper in the July number of ' The NaturaHst ' 

 on ' the Lower Carboniferous Rocks of Mill Gill, Wensleydale,' 

 calls for some criticism. 



Our present knowledge of the palaeontology of the Yoredale 

 Series of Wensleydale does not warrant the conclusions which 

 he formulates. He seems to have neglected, or dismissed with 

 a casual allusion only, the important facts of faunal distribution ; 

 and he has exaggerated the significance of isolated occurrences 

 of single, and often unimportant, members of a fauna. 



For example, he regards the occurrence of Posidonomya 

 becheri in the Shales above the Great Scar as absolute evidence 

 that the beds in which it occurs may be correlated with the 

 becheri beds at the base of the Pendleside Series. This, I feel 

 is not permissible for two reasons : — First, that Posidonomya 

 becheri is known to occur in Derbyshire at a much lower level 

 than the Pendleside Series, and second, the Pendleside Series 

 is zoned by a series of Goniatites. In one of the zones Posidonomya 

 becheri occurs in great abundance, but the important factor is 

 the fauna associated with it, and not the occurrence of the 

 species with a totally different fauna. If P. becheri can be 

 shown to occur in the true Yoredale Series with Nomismoceras 

 rotiforme, and the associated fauna, then, and then only, 

 will that lamellibranch indicate a definite horizon, and in a 

 secondar}^ sense be useful for purposes of correlation. 



Mr. Cosmo Johns lays stress on the occurrence of Ctenodonta 

 IcBvirostris and Stroboceras sulcatus in shales above the Great 

 Scar Limestone, with the comment — ' Their occurrence so near 

 the level of Posidonomya becheri is significant.' In the first 

 place, objection may be taken to his assumption that this 

 horizon is the level of P. becheri ; and secondly I would ask of 

 what horizon are these two species significant ? C. IcBvirostris 

 is known from many horizons, (Lower Carboniferous Limestones 

 to Coal Measures), and Stroboceras sulcatus has a known range 

 from Upper Dibunophyllum to Millstone Grit inclusive. I ask, 

 therefore, what possible significance these two species can have 

 on correlation ; both of them are known in a definite litho- 

 logical succession to occur below the zone of Nomismoceras 

 rotiforme. 



1910 Aug. I. 



