Vol. 62.] OKDOTTCrAN OF WESTEEN CAEEMAETHENSHIEE. 629 



south of it, is an east-and-west fault, which brings the Dicrano- 

 g?*aptus-Beds against Upper Bala rocks. The structure is made 

 tolerably clear by several useful exposures at and near Maeslan 

 and along the Penygraig lane, where the fold and fault are seen in 

 section. 



The black shales are much exposed at Llanddowror, particularly 

 near the Rectory, 1 along the old road, and up the Maeslan lane. 

 The character of the rock is fairly constant, and fossils are 

 moderately plentiful. The section at the Rectory has yielded : — 



JDiplograptus foliaceus, Murch. 

 Climacograptus tubuliferus, Lapw. 

 Climacograptus perexcavatus, Lapw. 

 Glossograptus sp. 

 Dicellograptus sp. 



Dicranograptus Clingani. 

 Corynoides curtiis, Lapw. 

 Holopella sp. 

 Orthoceras. 

 Discina: etc. 



From Llanddowror Bridge, some distance up towards Pentre- 

 howel, there is a very instructive exposure. Here can be seen the 

 gradual upward passage of the black shales to the Bala-Limestone 

 stage above. The shales become increasingly arenaceous : thin 

 bands with crinoid-ossicles, etc. become frequent ; Oriliis and other 

 brachiopods, as well as cephalopods, make their appearance. The 

 lower limestone-bands have lost their lime, and have assumed the 

 character of a light greyish-buff sandstone : but on the brow of the 

 hill the rock is still strongly calcareous. 



The lane leading to Faynor discloses a small section in the black 

 shales coming out under the Bala Limestone of Llanddowror Quarry. 

 They are here faulted against Upper Bala Beds. (See fig. 7, p. 628.) 



Another strip of DicranograptusShales extends from near Talfan 

 Lodge to Cwmcaedu, and is faulted against Upper Bala both on the 

 north and on the south. (Near Talfan are seen traces of mining 

 operations in these beds — presumably another endeavour to find coal.) 



In the dingle south-west of Faynor, the black shales are let out 

 by one of the numerous faults which traverse this locality, but the 

 outcrop is of very limited extent. 



(2) North of the Anticline. — From Pant-yr-hendref Quarry 

 to a point 100 yards north of Mydrim, there is almost a con- 

 tinuous road-section across the Dicranof/rctjrtus-Be&s. For conveni- 

 ence in the field, these beds are divided into three subgroups, 

 according to their lithological characters : — 



a — Black shales, weathering into various shades of buff and yellow ; 



(3 — Black shales, with lenticular iimestone-bancls ; 



y— Black slaty shales which crumble on weathering, but do not bleach. 



This subdivision will also, to some extent, hold good paheonto- 

 logically, inasmuch as the assemblage of fossils varies concurrently 

 with the lithological changes. In the buff-yellow beds graptolites, 



1 A short distance east of the Eectory a level has been driven into these 

 shales in search of coal. 



