FAUNAL SUCCESSION OF THE UPPER BERNICIAN 



621 



Stratigrapliical Character. 



The Great Limestone in the south of Northumberland 

 closely approaches a thickness of 50 feet, consisting of a thick 

 and massive stratum of limestone of 19 feet ("Main Post") 

 succeeded by a series of thin beds separated by shale 

 ("Tumbler Beds.") In Mid-Northumberland although reduced 

 in thickness the bed is more compact and freer from argillaceous 

 intercalations, but it again thickens and becomes more shaly 

 towards the northern boundary of the county, where it is 

 known as the Dryburn Limestone. At Beadnell the limestone 

 is strongly dolomitized. 



Faunal Diagnosis. 



Corals : — Dibunophylliim^ IConi?ickophyllum and Diphy- 

 phyllnrn reach their numerical maximum in this bed and dis- 

 play marked specialization and variation. Lonsdaleia dnplicata 

 and var. cotiaxis are common and widely distributed, and are 

 restricted to the Great Limestone. 



Brachiopods : — No very distinctive forms. Latissimoid 

 Frodiicii, (Prod. ^ and variants) Spirifer trigo?mlis, Retiadaria 

 lineata, Martinia. glabra and Athyris planosnlcata very 

 plentiful. 



Faunal List. 



Dibunophyllum muirheadi, Nich. & Thom. 

 and vars. ... 



Dibunophyllum muirheadi, var. D.splendens, 

 Nich. and Thom. 



Dibunophyllum near <^, Vaughan 

 Dibunophyllum : Cyathophylloid, Campo- 



phylloid and other variants ... 

 Cyclophyllum aff. pachyendothecum, Thom. 



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