The Upper Silurian rocks of the Gutterford Burn, in the Pentland Hills, have for some time been known to contain Eurypterid remains, but the fossils procured from these beds—chiefly owing to the exertions of Mr Hardy of Bavelaw Castle, and Mr Henderson, late Curator of the Phrenological Museum—have never been submitted to a thorough examination. When, therefore, by the kind permission of Sir R Murdoch Smith, Director, and Dr E. H. Traquair, Keeper of the Natural History Collection in the Edinburgh Museum, I was given an opportunity of examining Mr Henderson's collection, which was acquired by the Museum some years since, I entered upon the work with the expectation of finding some new and interesting forms which would repay description. My expectations in this respect have been more than fulfilled, as the collection has yielded five undoubtedly new species, one of which I have made the type of a new genus. If to these one adds at least two other new species which are in the collection of Mr Hardy of Bavelaw, and which I hope to have the pleasure of examining and describing at some future time, one is justified, I think, in saying that the Gutterford Burn is unequalled among Eurypterid localities with regard to the variety of forms it has yielded. Unfortunately the bed which has yielded these specimens is limited in extent, and further work on it would entail quarrying operations on a somewhat extensive scale.