224 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



II. Geology. 



The divisions in the Carboniferous Limestone series of Ireland, though some- 

 times fairly well marked lithologically, are of doubtful value for purposes of zonal 

 palaeontology, as it is a question whether the " Lower," " Middle," 1 and "Upper" 

 divisions, as constituted, were actually synchronous throughout the country, or 

 whether they may not have represented deposits of different character accumulated 

 simultaneously in different districts, and depending upon the diverse physical 

 conditions for their dissimilarity, — in fact, upon such variable results as might have 

 been produced by shallower or deeper water. 



As regards the beds above the so-called Upper Limestone, we have it on the 

 joint authority of Dr. Wheelton Hind and Mr. J. A. Howe 2 that certain beds in the 

 counties of Dublin and Limerick, at Westown 3 and on Foynes Island 4 respectively, 

 belong to the Upper Limestone Shales, or Pendleside Group. The characteristic 

 fauna found in them is held to supply " strong presumptive evidence of this view." 

 It should be added that the beds at Westown were recognised by the officers of the 

 Geological Survey to belong to the horizon now claimed for them ; those of Foynes 

 Island were, however, assigned to the Coal Measures. The species here tabulated 

 are in the Dublin Museum of Science and Art, in the Geological Survey Collection. 



The fauna at Westown comprises the following species : 



Avictdopecten papyracexis. Lunulicardium \_Footi~\. 



„ variabilis. Goniatites crenistria [Glyph, spirale^. 



Posidonomya membranacea. ,, Listeria 



[Posidoniella hevis?.] 5 Orthoceras [Steinhaueri]. 



Dithyrocaris. 



1 Called also " Carp," a local term originally employed by Kirwan. This rock is a dark-coloured, 

 or black, earthy limestone of a shaly or flaggy character. 



3 ' Quart. Journ. Geol. Soc.,' 1901, vol. lvii: " On the geological succession and palaeontology of the 

 beds between the Millstone Grit and the Limestone-Massif at Pendle Hill, and their equivalents in 

 certain other parts of Britain," p. 376. 



3 'Mem. G-eol. Surv. Ireland, 1 Expl. sheets 102 and 112, 2nd ed., 1875, p. 60. 



1 Ibid., Expl. sheet 142, 1860, pp. 8—15. 



5 The names between square brackets were added by Dr. Wheelton Hind. 



(i The specimens labelled " Coal Measures, Westown, co. Dublin — Goniatites Listeri," are too 

 much crushed to be specifically recognisable, but there are features in them which would amply suffice 

 to exclude them from that species ; one of these is a very distinct spiral groove or sulcus in the outer 

 whorl, recalling Glyphioceras bilingue ; the inner whorls are transversely ribbed. There are other 

 fragments on the surface of the shale with tubercular ribbing; these last may have suggested affinities 

 with Gastrioceras Listeri, but I am unable to confirm this view, the presence of the sulcus being fatal 

 to it and rather supporting the idea of a species with compressed whorls. No trace of the suture-line 

 is seen in any of the specimens that I have met with in these shales. 



