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PBOF. W. J. PUGII OX THE GEOLOGY OE THE [vol. lxxix, 



are represented by the outcrops of the Pont Erwyd Stage at 

 Derwenlas and Pant yr On, west of Pennal, respectively (see 

 tig. 5, below). 



There is a certain amount of minor folding, as revealed, for 

 example, by the outcrops of the Pont Erwyd Stage between Taren 

 y G-esail and Cwm Cadian ; but this appears to die out northwards. 

 There is little doubt that, from the point of view of geological 



Fig. 5. — Sketch-map illustrating the general geological structure 

 of the area oetiveen Corris and .Machynlleth. 



structure, the area is much less complex than that described 

 farther south about Machynlleth. 



All the folds in the Corris area show a well-marked southerly 

 pitch, as opposed to the northerly pitch at Machynlleth. When- 

 ever it is possible to take direct observations of the pitch, the 

 amount appears high; for example, when the outcrop of the zone 

 of Glyptograptus persculptus crosses the axis of the Corris 

 Anticline at Cwm Cadian, the pitch is about 35°, and again where 

 the well-marked grit-band in the Garnedd-wen Beds crops out on 



