The curious fossil which is here described and figured was discovered in a quarry about 50 yards north-west of Capel Horeb on the main road between Llandovery and Brecon (fig. 1). Most of the rocks of the quarry consist of thickly bedded, bluish-grey, highly micaceous sandstones (Tilestones) of Lower Downtonian age, which locally approach quartzites in composition. Many calcareous bands of fossils are intercalated with these Tilestones. The fossil fauna of this quarry and of others in the immediate neighbourhood has been noted and recorded by several workers, including Dr. L. D. Stamp and, more recently, Mr. S. H. Straw, who records the following fauna from this horizon:— Cornulites serpularius Sclotheim. Small Rhynchonellid. Cucullella antiqua (J. de C. Sowerby). Grammysia extrasulcata Salter. Modiohpsis complanata (J. de C. Sowerby). Bellerophon trilobatus (J. de C. Sowerby). Holopella obsolete (J. de C. Sowerby). Platyschisma helicites (J. de C. Sowerby). Orthoceras sp.Kloedenia (Beyrichia) wilckensiana (Jones). Fragment of a fish spine. The plant recorded in this communication has been obtained, not from the sandstones which occupy the major part of the quarry, but from a lenticular patch of gritty micaceous shales which is interbedded with them (PL XLIII, fig. 1). The lenticle is bounded by a lighter-coloured zone, 4 inches wide, of fine-grained