676 



MISS E. M. E. WOOD ON THE 



[Nov. 1906, 



gravel-pit, on the hillside half-a-mile due north of Stay-a-little 

 village. Similar forms were detected in the small stream farther 



south near the farm of 

 Ddwynant - gerig, about 

 150 yards below the 1-foot 

 grit-band, at the top of the 

 section which here marks 

 the base of the Talerddig 

 Group. 



(ii) Crygnant-Valley 

 Section. 



A longer and fairly- 

 continuous section of the 

 various groups, from the 

 top of the Nant-ysgollon 

 Shales to the top of the 

 Gelli Shales, is exposed in 

 the valley of the Cry gn ant, 

 which rises within half-a- 

 mile of Tarannon Farm, 

 and joins the Twymyn near 

 Pennant. 



A good section of the 

 INant-ysgollon Shales, from 

 the summit to the base, is 

 shown in the gorge east 

 of Cwm Mawr, and the 

 junction with the under- 

 lying Dolgau Beds is 

 marked by small grey- 

 wacke - beds somewhat 

 similar to those exposed 

 along the Tarannon River. 

 These shales have yielded 

 the characteristic Wen- 

 lock graptolites. 



Several good exposures 

 of the various divisions of 

 the Dolgau Group are seen 

 in the upper part of the 

 valley ; while the Talerddig 

 > ^ ^>^ Grits form a conspicuous 



^ feature in the bed of the 



stream for some 200 yards above Pont Crygnant. The shales in 

 the lower part of the Talerddig Group are too highly cleaved to 

 afford satisfactory palseontological evidence ; but, so far as one can 

 judge, the boundary-line between these beds and the underlying 

 Gelli Shales is approximately at Pont Crygnant. 



