Discussion on the submarine eruption and emplacement of the Lower Rhyolitic Tuf Formation (Ordovician), North Wales, Journal, Vol. 143, 1986 pp. 411-424, and reply = Discussion sur l'éruption sousmarine et l'emplacement de la base de la Formation Tuf rhyolitique (Ordovicien), Pays de Galles nord, J. geol. soc., GBR, vol. 143, 1986, pp. 411-424ORTON, G; HOWELLS, M. F; REEDMAN, A. J et al.Journal of the Geological Society (London). 1987, Vol 144, Num 3, pp 523-525, issn 0016-7649Article