448 Dr. Wheelton Hind 8f John T. Stohbs-^ 



Still higher in the series, Morton's ' Upper White Limestone ' has- 

 practically the same fauna as the beds immediately below, and hence 

 no palseontological line can be drawn between them. 



The ' Upper Grey Limestone ' of Morton is much richer in species 

 than the beds below, and is characterised by the abundance of 

 giganteid Producli and Spirifer bisulcatus, Sow. Morton's list is 

 a large one, containing 98 species of Brachiopods, Lamellibranchs, 

 Corals, Echinoderms, Polyzoa, and fishes.* The Lamellibranchs 

 passed through the hands of one of the writers, and were determined 

 by him as — 



Conocardium aliforme, Sow. Tinna flabell'xformis. Mart. 



Edmondia sulcata (Phill.). Frotoschizodus impressiis, De Kon. 



Leiopteria sp. Sanguinolites clavatus, E. Eth., jun. 

 Lithodomus lingualis (Phill.). 



With regard to the rest of the fauna, it has a distinctly Visean 

 facies, and indicates the upper part of the Carboniferous Limestone. 

 We collected the following Corals in situ from a bed nearly at the 

 top of the Ty-nant ravine below the yellow calcareous shales. 

 Corals are present in great abundance : — 



Cijathophylhun cf. regium, PMll. L. Portlocki (Bronn). 



Dibunophijllum sp. Lonsdaleiaforiformis, Lonsd. 



Lithostrotion ensifer, E. & H. i. rugosa, M'Coy. 



L. irregulare (Phill.). Phillipsastrcea radiata, E. & H. 



L.juncemn (Flem.). Sgritigopora &^. 



Morton also quotes, amongst others, Aulophylhim, Axophyllum, 

 several species of ClisiopliyUum, Cyclophyllum jfungites, KonincJco- 

 phyllum, ZapJirentis Bowerhanhi, Z. cylindrica, and Z. EnnisMUeni — 

 all of which, with the exception of Zaphrentis cylindrica (= Caninia), 

 we should expect to occur at this horizon. 



The horizon of this coral band all over North Wales is definite, 

 and marks out a time-zone of great importance, not only locally, but 

 one which can be perfectly correlated with the D, zone of the Bristol 

 and Mendip areas, so ably vporked out by Dr. A. Vaughan.^ 



In the Eglwyseg ridge the coral zone is succeeded by yellowish 

 calcareous shales, which in turn are overlain by a whitish limestone 

 with giganteid Prodncti and crinoids. This bed, we suppose, is the 

 top of Morton's Carboniferous Limestone Series, but it may possibly 

 belong to the lowest beds of his Cefn-y-Fedw Sandstone, which he 

 terms * the sandy limestone.' Above this limestone Morton 

 describes "a bed of dark grey limestone, 11 feet thick .... 

 It contains numerous encrinite stems with Frodiictus giganteus, 

 P. semireticulatiis, and P. Cora, and is succeeded by yellow flaggy 

 sandstones containing annelid tracks." The fact that P. giganteus 

 occurs here militates against any subdivision at this horizon. 

 If one feature comes out strongly all over the British Isles and 

 Belgium it is that P. giganteus characterises the upper beds of the 

 Carboniferous Limestone Series, and that the faunal change only 

 comes on when this shell disappears, whilst from the stratigraphical 



' G. H. Morton : " Carboniferous Limestone of Anglesey," pp. 52, 64. 

 2 A. Vaughan: Q.J.G.S., vol. lii, pp. 181-307. 



