vol. 69.] the pembrokeshire coalfield. 277 



Discussion - . 



Dr. Arbek desired to congratulate the Author on the very 

 considerable additions which he had made to our knowledge of 

 the fossil flora of South Wales. The new species described by the 

 Author were of interest, especially those referred to the genus 

 Linopteris. As the speaker had pointed out some years ago, the 

 species of this genus mimic in habit those of Neuropteris in an 

 extraordinary degree. Among the new species of Linopteris 

 described by the Author appears to be the long-expected homceo- 

 morph of Neuropteris scheuchzeri Hoffm. 



The fact that all the plants described by the Author indicated a 

 Middle Coal-Measure horizon was certainly a remarkable conclusion;, 

 but the speaker felt less surprised at this result, now that the 

 horizon of the beds in the Forest-of-Dean Coalfield on the eastern 

 side of the great South "Wales Coalfield was known. So far, it 

 would appear safer to assume that the Pembrokeshire, South 

 Wales, and Forest-of-Dean coalfields were unrelated areas, except 

 tectonically. 



The point raised by the Author with regard to the possible 

 absence of true Millstone Grits in Pembrokeshire was certainly in 

 keeping with recent conclusions as to the absence of this horizon 

 in the West-of-England coalfields ; but, as the Author doubtless 

 admitted, further proof of this contention must be forthcoming 

 before the matter could be regarded as settled. 



Prof. 0. T. Jones associated himself with the previous speaker in 

 congratulating the Author on a valuable and interesting piece of 

 research, carried out in a region of great difficulty. While not 

 desiring to criticize the Author's work, the speaker wished to point 

 to some of the possible consequences of the investigation. It was 

 suggested that the Millstone Grit yielded plants of Middle Coal- 

 Measure age. In many parts of Pembrokeshire it was clear that 

 there was an unconformity at the base of the Millstone Grit, so that 

 it was conceivable that higher portions of the Upper Carboniferous 

 might thereby rest upon Carboniferous Limestone. Against this 

 supposition there were several facts : — (1) In other parts of Pem- 

 brokeshire there was a close connexion between the higher beds of 

 the Limestone and the basal members of the Millstone Grit, thus 

 rendering it improbable that a physical break existed there ; 

 (2) The Millstone Grit of Pembrokeshire was exceedingly similar in 

 its succession of lithological characters to that of the northern out- 

 crop of the coalfield farther east (Carmarthenshire and Glamorgan),, 

 where strict conformity prevails, and a perfectly gradual transition 

 occurs between the two formations. 



Either, therefore, the Millstone Grit of Carmarthenshire and 

 Pembrokeshire are of the same Middle, Coal-Measure age, and 

 the representatives of the underlying Lower Coal Measures must 

 be looked for among the Carboniferous Limestone Series; or they 

 are of different ages, in which case the two similar formations 

 would be homotaxial but not contemporaneous : or, again, the 



