FAITNAL SUCCESSION OF THE UPPER BERNICIAN 633 



Dibuuophylliim <^ Vaughan. — This form, which differs from 

 Dibuuophyllum 9 m the length of the minor septa that 

 traverse the external area, and in the more strongly packed 

 vesicles, as well as in its narrow corallum, occurs in the Great 

 Limestone, and has been also obtained from a bed which is 

 probably the Redesdale. In the South-West Province the 

 species is most abundant in Di, but extends to D2. 



Dibunophylliitii nmirheadi mut. (cf. Dibunophyllum ij/ 

 Vaughan). — This species is characteristic of the Fell Top 

 Limestone. Compared with the type species the form is small 

 and conical. The central area is typically Aspidophylloid, 

 having a conspicuous plate projecting into the fossula and 

 abruptly terminated before reaching the opposite side of the 

 area. The lamellae are conspicuously shortened. The external 

 area is closely packed with vesicles, and the minor septa 

 are longer than in the typical form of D. midirheadi, although 

 never reaching the medial area. Dibunophyllum \J/ differs in 

 having longer minor septa, which traverse the whole external 

 area, and less shortened lamellae. 



Aspidophyllum sp. — A typical Aspidophyllum (with shortened 

 lamellae, an indistinct mesial plate, and septa separated off 

 into groups by wider interspaces) occurs in the Stamfordham 

 Limestone at Corbridge. 



Cyclophylliim aff. pachyendothecum. — The central area is 

 enclosed by a loose wall, and is not so strongly cuspidate as 

 in C. pachyendothecum, Thomson. 



A Clisiophyllid of Cyathophylloid habit. — Central area 

 not distinctly marked off from the medial area, simple and 

 Dibunophylloid, with very inconspicuous tabular intersections 

 and a few irregular lamellae. Medial area broad and traversed 

 by long, thickened, close-set septa ; regularly spaced inter- 

 sections in the interseptal spaces. External area narrow and 

 occupied by thin extensions of the primary septa and by 

 thin minor septa. Very minute vesicles occupy the septal 

 interspaces ; consequently, when mineralized, the external area 

 appears as a dense narrow ring in which the true structure is 

 obscured. Occurs in the Robsheugh Limestone. (Plate xvi., 

 fig. 6). 



