bionomy of the eurypterids, and to note also the change from an unquestioning assumption that the habitat was marine, to doubt and finally to opposition to the old idea.
Mitchell considered the form which he found in Westmoreland, New York, to be the impression of a catfish and so placed it under the genus Silurus, noting that the nearest living relative was the electrical silure of the Nile (180). He had no idea of the great age of the fossil, but supposed it to have been the remains of a fish which had lived in the Mohawk which was then generally believed to have been dammed so that the river waters and their fauna spread over a wide area. It is curious to see that the first man to find a eurypterid should, without any clear idea of its age or its true nature, have supposed that it lived in a river. This was mere speculation on his part and of no real significance. In 1825, however, Dekay, recognizing its true relation to the arthropods, established a new genus, Eurypterus, for it. He considered it most nearly related to the genera Apus, Binoculus and Lepidurus among modern forms, and placed it with the crustaceans of the order Branchiopoda. He mentions no other fofssil associates, nor does he make any statement concerning the habitat, but he evidently considered it marine, for had he not, it is only natural to suppose that he would have made some statement to that effect, since it would have been a new and, indeed, a startling idea to advance. In 1841 Conrad, writing of the Eurypterus from the Bertie says (44, 38): "It has been suggested that this genus was of fresh water origin, but the presence of fucoids in the same stratum where the Eurypterus occurs, and the absence of the slightest evidence of a fresh water deposit in any part of the Silurian system, leave no room to doubt that this singular crustacean inhabited the sea." Conrad did not state who the bold spirit was that made such an original suggestion and his reasons for rejecting this explanation are unconvincing, because so-called fucoids are not necessarily marine, and non-marine deposits are now extensively known from the Siluric. Furthermore, even if the "fucoids" prove to be graptolites, as now claimed by Ruedemann, a non-marine habitat for the Eurypterus is not precluded. All the early writers seem to have agreed to consign the eurypterids to the class of the Crustacea, and to maintain for them a marine habitat. It has taken many years of patient labor for the students of the anatomy of these organisms and of the taxonomic relations of the Eurypterida to the Crustacea, to Limulus and to the scorpions, to convince the geological world that the Eurypterida are
