A. Heard — The Petrology of tlie Pennant Series. 



83 



Upper Algal (?) Band. 

 Pot-holes Bed . 



Mudstone . 

 Spotted Beds 



Thin Mudstone 

 Roucrh Beds 



Calcite Mudstone 

 White Beds 



Algse (?) (Frizington) ; plants in the sandstone. 



Standard fauna, D2 corals abundant ; Saccammina 

 in upper beds. 



Mudstone unfossi'iferous ; plants in sandstone. 



Brachiopods particularly abundant in top beds ; 

 foraminifera abundant, large Textularia sp. 

 characteristic. Lon-sdaleia sp. [var. in which 

 many septa reach theca]. Litlwstrotion irregular e 

 Phill. abundant. 



No fossils. 



Typical Do-fauna abundant, with many lamellibranchs 

 in lower portion. Chonetes cf. cotnoide-s occurs in 

 band near base, and Girvanella sp. occurs 

 encrusting crinoid stems and coral fragments in 

 a band at the base and is found in the calcite- 

 mudstone immediately below. Chief associated 

 forms are: Produc*us edelburgensis Phill., 

 P. maximus McCoy, Chonetes compressa Sibly, 

 Pugnar pleurodon (Phill.), Spirifer bisulcatu-s J. de 

 C. Sow., Dibunophyllum 6 Vaughan, Caninia 

 dentimlata Thorn., Lotisdaleia floriformis (Mart.) 

 mut. nrassiconus S. Smith, Carcinophyllum sp., 

 Zaphrcntis sp., Cyathophyllum murchisoni Edw. & 

 H., and Lithostrotion irregulare Phill. 



Spirorbis-like annelids, Girvanella sp., and many 

 small gastropods. 



Brachiopods abundant in upper beds ; Productus 

 cora d'Orb. mut. Di, P. hemisphericus J. Sow., 

 Schizopjhoria resupxnata {^la.vt.),Cyrtina septosa (?) 

 Phill. A gastropod, Straparollus acutiis (Sby.), 

 is common. Corals abundant, especially in lower 

 beds, and typical of Dj : Cyathophyllura 

 murchisoni Edw. & H., Carcinophyllum SVaughan, 

 Dibunophyllum d Vaughan, Caninia cf. dcrbiensis 

 Vaughan, Lonsdaleia duplicata (Mart.), and a 

 Clisiopiiylloid LithoHrolion. 

 (To be continued.) 



The Petrology of the Pennant Series, East of the 



River Taff. 



By A. Heaed, 31. Sc, F.G.S., University College of South "Wales 

 and Monmouthshire. 



ALTHOUGH much geological research has been done on the Coal 

 Measures of South Wales, little detailed work on the petrology 

 of the series, east of the River Taff, has been published. This vrork 

 has been undertaken in the hope that the petrology of the district 

 may give a foundation for a reliable correlation or may give a clearer 

 conception of the conditions of deposition and the source of the 

 sediments than is obtained from a study of the coal-seams alone. 



The Coal Measures of South Wales are divided into three main 

 groups : the Lower Coal Series, the Pennant Sandstone, and the 

 Upi^er Coal Series. The upper boundary of the massive sandstone 

 series known as the Pennant Grit, is defined by the M}Tiyddislwyn 



