The shell to which I have given the above name is at present unique. It was found, a few years ago, in a quarry at Clane, in the county of Kildare, where I had for some time been in search of Cephalopod shells. It was associated with characteristic species of Carboniferous Limestone fossils, among which the following Nautiloid shells may be mentioned, viz. Solenocheilus dorsalis, Phil., sp., Asymptoceras cyclostomus, Phil., sp., A. Foordi, Hyatt, and an undescribed species allied to the last-named one. The marginal spines, at first obscurely seen in the matrix, at once attracted attention; and although one was broken off and lost in the quarry débris, the other was fortunately found in the fragment of rock struck off from the shell, and was then carefully developed and attached to the latter. Naturally very diligent search has been made since its discovery, and a sharp look-out kept for any further specimens of this interesting species, but so far without any result.