During the summer of 1877 I made a geological excursion, in company with one of my students, to the western part of our State, to examine the junction of the Upper Silurian (“Clinton” of the Ohio Survey) and the Cincinnati group of the Lower Silurian. Whilst thus engaged near Eaton, in Preble Co., my companion, Mr. Leven Siler, of that town, picked up and handed to me a slab bearing what appeared to be a mould of the well-known bark of the Lepidodendron, somewhat weathered. More careful examination confirmed the first impression, and convinced me that I had indisputable proof of the existence of arborescent vegetation of an earlier date than had hitherto been announced upon equally conclusive evidence.