412 



Dr. G. L. Elles— 



are easily recognizable, though somewhat finer in grain and with 

 more numerous mud stone bands. Overlying them come, as before, 

 the Phacops Mudstones, here slightly more shaly in character, 

 and containing one narrow, but definite, calcareous band, whilst 

 immediately above these in the place of the Hirnant Beds come 



N. 



Moelfryn 

 Sandstones.. 



Phacops 

 Mudstones. 



Lower 

 VaJentian» 



Fig. 3. — Sketch-map of Bwlch y gross. Scale 6 inches = 1 mile. 



Graptolitic Shales with a well-defined Lower Birkhill fauna, com- 

 prising : — 

 Monograptus atavus Jones (small Climacogrwptus rectangularis 



fragments). (His.). 



Dimorphograptus extenuatics Mesograptus modestus var. 



E. & W. diminutus E. & W. 



Climacograpius normalis. Lapw. 



This assemblage clearly indicates the suhzone of Monograptus 



