380 



MISS G. L. ELLES ON THE WENLOCK 



[May 1900, 



of Gaufron Uchaf, and along a cart-track south of the copse, these 

 were more fossiliferous, and yielded the graptolites enumerated in 

 Table I, col. M (p. 378). 



These calcareous shales are again exposed in the lane leading 

 down to Wern Fawr, arid at the bottom of it are seen to be 

 succeeded by hard flagstones. The flagstones are well exposed in 

 the quarry south-west of Neuadd, where certain bands are richly 

 fossiliferous, and have yielded fragments of trilobites and many 

 brachiopods, but no determinable graptolites. The beds strike £L 

 30° E., and occupy the greater part of the railway-cutting to the 

 north between Neuadd and Gaufron Isaf. 



Beds, which evidently succeed this flagstone-band, are exposed 

 in an old quarry south-west of Gaufron Isaf; they are somewhat 

 peculiar, since they consist of a series of calcareous-micaceous flag- 

 stones and sandstones, with bands of rotten limestone. The beds 

 have yielded Monograptus colonus, Barr. ?, M. Nilssoni, Barr., and 

 Dayia navicula, Sow. ?, and must therefore be regarded as 

 belonging to the Lower Ludlow Series : consequently, all the 

 beds which lie above them must also be of Ludlow age. 



The highest beds seen are hard, siliceous, and light in colour ; 

 they are exposed in a quarry beyond Wern Fawr, and are seen to 

 dip 60° north-westward. Precisely similar beds are also exposed 

 in a quarry south-east of Bryn Wood, where the dip is still 

 steeper ; and again in a quarry beyond Pen-y-rhiw, where the 

 dip is still very steep, but in a south-easterly direction. Conse- 

 quently, the central axis of the fold must be very near that locality. 



The succession in the north and north-west of the Builth district 

 may be summarized as follows (in descending order) : — 



T f Hard, light-grey, siliceous flags. 



.Ludlov Micaceous sandy shales with rotten limestone-bands. 



Calcareous flagstones with fossiliferous bands. 

 (6) Calcareous fissile shales with beds of flagstone. 

 =Zone of Cyrtograptus Lundgreni. 

 (5) Hard, grey, calcareous shales with graptolites. 



=Zone of Cyrtograptus rigidus. Feefc. 



Light-coloured flags, unfossiliferous 400 



(4) Grey calcareous flags and shales, with limestone- 

 concretions 300 



= Zone of Cyrtograptus Linnarssoni. 



(3) Soft shales with harder flaggy beds . 200 



= Zone of Cyrtograptus symmetricus. 



(2) Hard calcareous flagstones 300 



= Zone of Monograptus riccartonensis. 

 (1) Soft fissile shales alternating with flags. 



=Zone of Cyrtograptus MurchisonL 



Wenlock 

 Shales. 



(0) Section along the River Irfon. 



A little to the west of the town of Builth a magnificent? section 

 is exposed in the Biver Irfon, and in the summer of 1898 ex- 

 ceptional facilities were afforded for working it, owing to the 

 prolonged drought and the low state of the water. 



