86 MR. H. LAPWOTtTH ON THE [Feb. IQOO, 



(b) Esgair-rhiw. 



An excellent confirmatory section (fig. 3, p. 85) of the Gwastaden 

 Group occurs in the brook west of Esgair-rhiw Farm, about a 

 mile east of the typical section. The Cerig Gwynion Grits 

 (Aa) at the crest of the hill are here again found to overlie cleaved 

 Blue-black Shales, but reach a thickness of only about 100 feet. 

 Descending towards the stream, we pass over a few exposures of the 

 Micaceous Flags and Grits (Ab x ), dipping at 26° north- 

 westward. A short north- and-south fault is next crossed, and 

 we then enter the stream-section at the sharp bend to the west. 

 In some carbonaceous bands in the blue-and-grey Micaceous Flags 

 and Grits immediately below the hedge Climacograptus parvulus 

 and CI. normalis may be detected ; and some distance farther 

 down Diplograptus acuminatus also occurs. From the first hedge 

 above the path leading to Esgair-rhiw Farm to about 100 feet 

 below it, there is a fairly continuous exposure of the red-weathered 

 flags and shales. These yield the fossils enumerated above, to- 

 gether with Diplograptus modestus (?) and Orthoceras sp. The dip 

 of the beds is about 30°. 



A gap in the section probably takes the place of the Rottenstone 

 Beds, for the grey Diplograptus-modestus Flags (Ab 3 ) are- 

 well shown immediately above the hedge at the summit of the 

 copse, and for some hundred yards or so below. Immediately 

 south of this hedge, the flags contain Diplograptus modestus, and 

 from a calcareous band about 5 or 6 yards north of it I have 

 procured 



Orthis elegantula, Dalrn. 



testudinaria (?) Dalm. 



Favosites gothlandica, Fougt. 



Stenopora {Favosites) fibrosa, Goldf, 

 Atrypa sp. 



On the flat ground, and for a length of 300 or 400 yards 

 within it, not a patch of rock makes its appearance. A strike-fault 

 (shown in fig. 3, p. 85) crosses the centre of this blank, and at the 

 line of section has a downthrow of about 200 feet. 



In the trench for the Birmingham Aqueduct along the banks of 

 the stream south of Pen-y-bont road, about 300 yards east of 

 Cefn-Ceidio Hall, an excellent section of the Ddol Shales (Ac) 

 was laid open. The fossils obtained from the blue-banded shales in 

 the sides of the trench were in relief and in perfect preservation. 

 The forms detected included Monograptus communis, M. jimbriatus, 

 M. argutus, Diplograptus tamariscus, D. magnus, D. sinuatus, Cli- 

 macograptus rectangularis, CI. undulatus, and CI. normalis. All 

 these species are characteristic of the summit of the Zone of 

 Monograptus fimbriatus (Ac 3 ). 



The overlying Mudstones were not seen in the cutting itself, 

 but they are well exposed on the northern bank of the stream 

 east of Cefn-Ceidio. 



As this section is continued in a north-westerly direction through 

 the junction of the Pen-y-bank and Pen-y-bont roads, the ground 



