210 



G. L. Elles — Graptolitc Zones in Arenicj BoeJiS. 



■ (2) Eastern District. 



Furthei" east in South Wales, in the eastern part of the Haverford- 

 west district, Marr & Roberts ^ have indicated in their ' JJidymograptus 

 shales ' the extension eastwards of the zones of J). Murchisoni above 

 and D. bifidus below. And a collection of fossils made long ago by 

 the late T. Roberts, and now in the Sedgwick Museum, Cambridge, 

 seems clearly to point to the existence of the zone of D. extensus at 

 Talfan, near VVhitland, since the beds there have yielded D. extensus, 

 Hall, D. nitidus, Hall, Tetragraptus serra, Brong,, 2\ Ainii, Lapw., 

 T. Ileadi, Hall, Dendrograptus fruticosus, Hall,' Callograptus per- 

 sculptus, Hopk., and C. Salteri, Hall, 



In the Carmarthen district Crosfield & Skeat" have mapped the 

 zones o{ I). Murchisoni and D. bifidus over a considerable tract of 

 country, and the fauna of the shales of Hafod Wen, which they have 

 courteously permitted me to examine, containing as it does both 

 D. hirundo and B. nitidus, leads me to believe that the Hafod Wen 

 shales represent the zone of D. hirundo; the beds of Glan Pibwr 

 possibly indicate the still lower horizon. 



Correlation and Conclusions. 



The correlation of the Welsh Arenig Series with beds of other 

 areas is indicated in the above table. 



The facts noticed about the beds would lead us to suspect that 

 the series is incomplete in Wales, and a comparison with other 

 areas tends to confirm this suspicion. 



^ Loc. cit. - Loc. cit. 



