598 ME. D. C. EVANS ON THE ORDOVICIAN [Nov. I906, 



Between the years 1885 and 1899, I got together a fairly-large 

 and representative collection of fossils. The graptolites were 

 exhibited at the meeting of the Royal National Eisteddfod held 

 •at Merthyr Tydvil in the summer of the latter year ; and again, 

 a general collection was exhibited at the meeting held at Llanelly 

 in 1902. 



A portion of the area is now being surveyed by the officers 

 of H.M. Geological Survey — Messrs. T. C. Oantrill, B.Sc, and 

 H. H. Thomas, M.A., B.Sc. ; with them I have had the pleasure 

 of going over much of the ground, and to them I am indebted for 

 much kind encouragement and valuable advice. 



(2) References. — 



Richard Fenton. ' Historical Tour through Pembrokeshire' (Appendix 



No. 17) 1811. 4to. London. 

 The Geological Survey (1842) Sheets xli & 13. 

 R. I. Murchison. 'The Silurian System' 1839. 

 H. Maclalciilan. Trans. Geol. Soc. ser. 2, vol. vi (1842) p. 557. 

 John Phillips. ' The Malvern Hills compared with the Palasozoic 



Districts of Abberley, &c.' Mem. G-eol. Surv. vol. ii, pt. i (1848). 

 J. W. Salter. 'Monograph of the British Trilobites' Palseont. Soc. 



1864-1885. 

 Thomas Davidson. 'Monograph of the British Fossil Erachiopoda' 



Palseont, Soc. 1851-1886. 

 Charles Lapwortii. ' On the Geological Distribution of the Rhabdo- 



phora' Annals & Mag. of Natural History, ser. 5, vol. iv (1879) 



pp. 333, 423 ; & vol. v (1880) pp. 45, 273, & 358. 

 J. E. Marr & T. Roberts. ' The Lower Palaeozoic Rocks of the 



Neighbourhood of Haverfordwest ' Quart. Journ. Geol. Soc. vol. xli 



(1885) p. 476. 

 Thomas Roberts. ' Notes on the Geology of the District West of 



Caermarthen' Quart. Journ. Geol. Soc. vol. xlix (1893) p. 166. 

 Miss M. C. Crosfield & Miss E. G. Skeat. ' On the Geology of the 



Neighbourhood of Caermarthen ' Quart. Journ. Geol. Soc. vol. Hi 



(1896) p. 523. 

 Miss G. L. Elles & Miss E. M. R. Wood. ' Monograph of the British 



Graptolites ' Pt. i. Palaeont. Soc. 1901-1902. 



II. General "Remarks. 



(1) Physical Structure. — The dips and the general relation 

 and arrangement of the various rocks prove that the area is, in the 

 main, a denuded anticlinal fold of considerable extent, with an east- 

 and-west axis. The ground has, however, been much complicated 

 by inner and minor folds accompanied by a great deal of faulting 

 and crushing. There is abundant evidence that the main fold was 

 thrown over to the south, and that further complications have been 

 brought about by subsequent fractures and thrusts among the 

 minor, subsidiary folds, with the result that, in some instances, 

 older beds have been brought to the surface and pushed some 

 distance over newer ones. Examples of overfolding and thrusting 

 are numerous and perplexing, especially when they occur in shales 

 of Tetragraptus- and Didymograptus-hifidus age. 



