In the Museum of Practical Geology, London, is a remarkable specimen, marked , which the late Mr. J. W. Salter referred to, in the ‘Quart. Journ. Geol. Soc’ vol. xix. 1863, p. 92, as “a huge bivalve Crustacean,” … “with a carapace 7 inches long,” giving it the name “Dithyrocaris pholadomya.” It is in a dark micaceous sandstone, from the “Carboniferous Shales” (or Lower Limestone of the Carboniferous-Limestone series), of Berwick-upnn-Tweed. In the “Catalogue of the Collection of Fossils in the M.P 6.,” 1865, p. 116, it is referred to as “Dithyroearis pholadiformis”; but whether or no this specific name was an alteration made by Mr. Salter himself is doubtful.