On the Fossil Crustacean found in the Magnesian Limestone of Durham by Mr. J. Kirkby, and on a New Species of Amphipod

Abstract

In January, 1857, a paper by Mr. Kirkby was read before the Geological Society*, on “some Permian Fossils from Durham,” in which a few fragments were described as the remains of an extinct Crustacean. Some drawings of these were kindly submitted to me previously to their publication. One series I regarded† as being probably from the anterior portion of an Isopod; and the remainder I considered as not belonging to the same animal, but as parts of an Amphipod. I have recently (since the reading of this paper) been allowed, through the kindness of Mr. Kirkby (to whom I applied in accordance with a suggestion from the Council of the Geological Society), the advantage of examining the original specimens of Prosoponiscus problematicus , together with others that have been discovered since the publication of his paper. Having thus a favourable opportunity of reconsidering an opinion which was given from an examination of drawings only, I have been enabled to make out some points not portrayed in the drawings, which enable me to arrive at a more satisfactory conclusion. The specimens are the anterior and middle parts of an Amphipod; and none belong to an Isopod, as I at first informed Mr. Kirkby‡. To show with any amount of certainty the correctness of this hypothesis, it is necessary that I should demonstrate, in recent Crustacea, an approximation of structure to that of the fossil. Assuming that, if certain known parts of an unknown animal agree in character with those homologically the sae