156 



WALTER KEEPING ON THE 



pitous mountain-sides, from 500-1000 feet high, and I cannot esti- 

 mate the group at less than 2000 feet. 



Fossils are almost entirety wanting in this series, except, I be- 

 lieve, near the base, where I would place the rich beds of the 

 Morben Quarry, Machynlleth, and Cwm Symlog. The fauna is 

 intimately related to that of the Aberystwyth group, as indeed was 

 to be expected ; for the fossils of this latter group occur in its higher 

 part, not far removed, in serial order, from the Metalliferous-slate 

 fossil-zone. 



The worm-like and fucoidal markings, Nereites, the Pan Algal, 

 and the Nematolites are widely distributed throughout the series, 

 worm- trails being very characteristic. 



Other fossil localities are : — 



Llantrisant, with the large Pan Algal (Buthotrephis major) and 

 Nematolites tubularis, Keep. ; the Llyfnant valley, with Climaco- 

 grapsus scalaris, His. ; Dynryn Castell, with Climacograpsus scalaris, 

 worm-tubes, and the Nematolites, also some of the shells recorded 

 by Sedgwick ; and Steddfa Ghirig (west of), with Monograptus Sedge- 

 wicTcii, Portl., M. tenuis, Portl. ?, Climacograpsus scalaris, His., and 

 Ortlioceras. Above Taliessin, fragments of dendroid Graptolites and 

 Nematolites tubularis occur ; and the latter is also found at Llantri- 

 sant, Ty Llwydd, on the Eheidol, and elsewhere. 



Richer localities are : — 



West of Lisburne Mine, Ystwyth Valley. 



Pastrites ? Climacograpsus scalaris, His. 



Monograptus Sedgewickii, Portl. Nereites Sedgwickii, Murch. 



spiralis, Gein. Buthotrephis. 



lobiferus, M'Coy, 



Garthen Valley, Melin Newydd. 



Monograptus Sedgewickii, Portl. j Orthoceras, sp. 

 Climacograpsus scalaris, His. 



The numerous metalliferous veins (lead and silver) in the rich 

 mining- districts of Cardiganshire are almost confined to this set of 

 beds ; hence the name here given it. 



3. The Plynlimmon Group. — As we ascend the mountain-slopes 

 along the valley of the Eheidol, above Pont Erwyd, we meet with 

 the rocks of the upper grit series, which form the upper part of the 

 Plynlimmon mountain. Around Garn Pach some of the grit-beds 

 are seen, of rather coarse type, sometimes assuming a very grani- 

 toid aspect, there being a profusion of felspar crystals and large 

 blebby quartz grains. The felspar crystals may be of large size ; and 

 some of them are perfectly preserved and glassy. Doubtless the 

 rock is the direct result of the degradation of an ancient acidic 

 igneous rock. 



Conglomerate beds, consisting of pebbles of white quartzite and 

 vein quartz in a grit matrix, are also met with ; but they are few. 

 The group here is still, in the main, a slate series, some of the slate 

 being pale and papery, of the "pale-slate type." Iron pyrites is 



