Discussion

Abstract

Dr P. T. W arren said that Dr Rickards had been kind enough to mention the speaker's paper on the Scottish Wenlock, read to the Society four years ago; at that time he had predicted that the work then progressing in the Howgill Fells would answer many of the problems of the Scottish sequence and its correlation. This it had largely done, and Dr Rickards was to be congratulated on a meticulous piece of work which was a major contribution to Wenlock/Ludlow stratigraphy and correlation. The progression in Middle Wenlock cyrtograptids of the position of the first cladium, which the author described, was also found in the North Wales succession, under study by the speaker and his colleagues in the Institute of Geological Sciences; here the species involved were C. rigidus Tullberg, C. perneri Bouèek and C. ellesae Gortani. The author's upper and lower lundgreni Zones could be matched closely in North Wales (although thicknesses were approximately double those in the Howgill Fells) but succeeding these were about 800 ft of strata representing the ludensis [ vulgaris ] and lower nilssoni Zones. Both the ludensis and the upper lundgreni Zone contained calcareous mudstones—the approximate correlatives of the Wenlock Limestone of the Welsh Borderland; might Dr Rickards' lower lime-stone be correlated with these and hence be of Wenlock age? The possible discontinuity Dr Rickards conceded in his succession at the level of his basal Ludlow limestones (associated with slumped beds) took on particular significance when it was realized that his fauna from between