500 Dr. Wheelton Hind 8^ John T. Stobhs— 



fauna of Derbyshire, North Stafifordshire, and Yorkshire occurs, and 

 it is an important question as to what conditions determined the 

 paucity of species and genera at the same horizon in the Bristol area. 



The presence of Lonsdaleia^ Cyalhophylhim, and the smaller species 

 of Lithostroiion indicate the line which separates the Upper and 

 Lower Dibmiophyllum sub-zones in North Wales. 



Tlie upper part of the latter zone is characterised by important 

 corals which mark off a definite sub-zone, the importance of which 

 is great l)ecause these corals occur at the same horizon in other areas 

 in the Midlands. 



These corals are Cyathaxonia and a new form which Dr. Vaughan 

 has described as Amplexi-zaphrentis (Quart. Journ. Geol. Soc, 

 Yol. Ixii, p. 215). The history of the latter is of interest, as it was 

 on his determination of these specimens, which I knew came from 

 beds at the very top of the Carboniferous Limestone, to he Zaphrentis 

 Phillipsi that we doubted the value of the latter as a zone fossil. 



Externally this coral cannot be distinguished from a small 

 Zaphrentis, but sections demonstrate structural differences, the septa 

 in full-grown forms not reaching the centre and being attached to 

 the wall by broad bases. They possess tabulee with a fossula-like 

 depression. Dr. A. Vaughan has published figures of these corals, 

 op. supra cit. 



Both Cyathaxonia and. Amplexi-zaphrentis are abundant in the 

 upper beds of the Carboniferous Limestone and in the calcareous 

 shales at the base of the Pendleside Series with Prolecanites 

 compressus, at Bradbourne, Derbyshire, near Warslow and Wetton, 

 Staffordshire, in the banks of the Hodder near Stonyhurst, and also 

 at Whitewell, and immediately below the Posidonomya Becheri beds 

 in a little stream south-east of Hill Skelterton, near Cracoe. I have 

 also found them at the same horizon at Kainhall Quarry, Barnolds- 

 wick, and at the quarry half a mile south of Switchers and one and 

 a half miles W.S.W. of Hellifield. 



The range of Cyathaxonia and Amplexi-zaj)hrentis denotes the 

 passage beds between the Carboniferous Limestone Series and the 

 Pendleside Series. At Lady McLaren's Quarry, Prestatyn, they 

 lived on until Pterinopecten papyraceus appeared. 



In North Wales this passage series is complicated by the local 

 presence of the chert beds. The chert beds themselves contain but 

 few recognisable fossils beyond abundance of sponge spicules (vide 

 ante, p. 393), and they are immediately succeeded by the black 

 shale and limestones which represent the Pendleside Series iu 

 North Wales. We should expect a careful examination of these 

 cherts to yield Kadiolarians similar to those which occur in the 

 Culm Series of North Devon, which are probably of the same age. 



Just as the oncoming of the deposit of the thick mass of Car- 

 boniferous Limestone was gradual and gave rise to local differences 

 in the deposit, so the commencement of the deposition of the thick 

 shale series, the substitution of a detrital for a purely organic deposit, 

 produced divergences Which have made correlation somewhat 

 obscure. One fact, however, seems to become more and more 



