No complete list of the Stonesfield Fossils has been drawn up since 1855, when some remarks of mine on the Geology of the vicinity of Oxford appeared in the first series of Oxford Essays. During the last eleven years we have received from that rich locality many additional specimens, but not many species new to the University Museum. One has lately reached my hands which I hope will be of interest to the readers of the Geological Magazine, as adding something to the knowledge of a prevalent group of water-side insects, which had left witnesses of its existence through a very large range of Geological Time, viz. the Neuroptera, and specially the Libellulidœ.