424 



MR. A. WADE ON THE LLANDOVERY AND fAug. I91 I T 



If we follow the strike westwards as far as Guilsfield Brook, 

 it brings us up against a river-cliff consisting of the Powis-Castle 

 Conglomerate series. The whole of the Ordovician succession of 

 Moel-y -garth ends abruptly against Silurian rocks here in Guilsfield 

 Brook. Another huge fault, running north-east and south-west, 

 occupies the bed of the stream. The throw is to the north-west, 

 and is at least 2000 feet in amount. This fault may be appropriately 

 named the Moel-y-garth Fault. 



On this side of the valley, the Trilobite-Dingle Shales are not 

 again well exposed until Middle House is reached, half a mile north 

 of Guilsfield, where they are seen in the stream-section, although 

 they must occur under the drift and alluvium covering the valley- 

 floor. From this point they can be traced by Ceunant Mill to the 

 northern limit of the map. 



It is fairly certain that the lower beds of the Trilobite-Dingle 

 Group are of Llandeilo age; but there is no sufficient palgeontological 

 or lithological break in the succession to enable us to draw the 

 line. 



List of Fossils from the 

 Tkilobite - Dingle Shales. 



<v 



a5 







be 



bp 



He 



a 



s 



<D 



3 



P 



3 

 O 









-i-s 



a 







,o 











>> 









% 





-CSQ 



EH 



H 



Ph 



3 



X 











O 10 





j-£H3 









j-"rQ 





j^ &D 







ri 





3 



Ot- 1 





r be > 





a o 





1 bo 2 



o 



3- 





X 





X 





X 





X 





X 



X 



! 



X 





X 







i X 





X 





X 



... 



X 



::: 



Asaphus po wisi Murchison 



Dionide sp J ... 



Trinucleus concentricus Eaton , X 



Trinucleus concentricus, var. caractaci Murch. ... ... 



^Trinucleus concentricus, aff. var. portlocki Salter. 

 Trinucleus concentricus, cf. var. arcuatus Smith . ... 



Trinucleus intermedins, sp. nov X 



Trinucleus cf. lloydi Murchison ... 



Climacograptus schcerenbergi Lap worth I X 



Diplograptus (Amplexograptus) perexcavatus\ X 



Lapw. 



D. (Amplexograptus) arctus Elles & Wood j ... 



Diplograptus (Mesograptus) foliaceus Murch. 

 Diplograptus (Orthograptus) truncatus Lapw 

 D. (O.) truncatus, var. pauperatus Elles & Wood 

 D. (O.) pageanus, var. micracanthus E. & W. ... X 

 Sellerophon (Protoivarthia) bilobatus Sowerby . . . X 



Belleroplwn sp X 



Cgrtolites parvus Ulrich, var. carinatus nov. 

 Ctenodonta coarctica Phillips 



^Ctenodonta lingualis Phillips 



* Ctenodonta antiqzia Sowerby 



Ctenodonta cf. levata Hall 



Ctenodonta?^. ... 



Ortliis sp 



X 



* Fossils marked with an asterisk were collected by J. Bickerton Morgan. 



