On a new Genus of Eurypterida from the Lower Ludlow Rock of Leintwardine, Shropshire

T he specimen which forms the subject of this paper is in the Museum of Practical Geology, Jermyn Street, and through the kindness of Professor Huxley I have been permitted to describe it. Its discovery was referred to by Mr. J. W. Salter, in 1857 (under the MS. name of Limuloides ), in the ‘Annals and Magazine of Natural History,’ in a paper “On some New Palæozoic Starfishes,” but the genus has never yet been described (except by myself at the British Association, Bath, 1864). The great interest, attached to this new Crustacean is, that it appears to offer just the link we needed to connect the Xiphosura with the Eurypterida . Limuli , apparently differing but little as regards the carapace from the recent species of China and America, occur as early as the deposition of the Solenhofen limestone of Bavaria; and in the Coalmeasures of England and Ireland several species of Bellinuri occur, in which the cephalic shield is composed of the cephalo-thorax; and the segments of the abdomen if not anchylosed in all, are so in most. But in the specimen under consideration we have the cephalic, thoracic, and abdominal divisions still remaining distinct, and apparently capable of separate flexure. This important character at once separates it from Limulus and Bellinurus. I have on this account ( with the concurrence of Mr. salter ) considered his MS. name of Limuloides inappropriate as a generic appelation, and adopted the name of Hemiaspis (from ἥμισνς, half , and ἀσπìς, a shield ), reserving Mr. Salter's name of