Severa years ago I deduced from the distribution of the mammalian cave-fauna of Ireland that an unknown extent of Older Drift existed in the southern part of that country and that the end-moraine of the Newer Drift, bordering it on the north, ran somewhere to the south of the Central Plain. During a series of excursions into the Dublin and Wicklow Hills in the company of Mr. A. W. Stelfox, of the National Museum, Dublin, this moraine was readily detected skirting their flanks; subsequent researches led to its complete mapping from coast to coast. When this part of the field-work was complete, a remark made by Mr. Stelfox led me to the unexpected discovery that the moraine was already known to H. Carvill Lewis. Priority is, therefore, his. His map and conclusions, however, were based upon a very limited number of observations, made in the course of his various traverses of the country, where the railways chanced to cross the line of the moraine. He surmised that the moraine was continuous through these localities, and drew in its course from conjecture. It is consequently not surprising to find only the roughest agreement between his uncertain suppositions and the unequivocal results of this more careful survey of the moraine along its whole length. Carvill Lewis, moreover, erred in interpreting as the moraine certain other deposits, such as river-gravels, which bear no relation to it; and he went still farther astray by linking up with it a number of morainic features which