Page:The Habitat of the Eurypterida.djvu/68

 "Their adaptation to such conditions is paralleled today by such crustaceans as Apus and Artemia which not only thrive under rapid diminution of normal salinity but, by means of strongly protected eggs, even survive salt pan conditions which end in complete desiccation, as shown by their well known occurrence in desert lakes. The usual associates of the Siluric eurypterids are peculiar crustaceans whose nature emphasizes the reference above made. They are phyllocarids and ostracods and members of the strange family Hemiaspidae (Neolimulus, Bunodes, Hemiaspis, Pseudoniscus). This congeries of peculiar crustaceans seems to constitute a fauna especially adapted to, and therefore highly characteristic of, lagoon and estuary conditions.

"Thus while the earlier eurypterids were marine and their climacteric fauna euryhaline; their later habit throughout the Devonic and Carbonic led them finally into the fresh water.

"The succession of habitats is hence, according to our evidence, the reverse of that suggested by Chamberlin's hypothesis noted at the beginning of this discussion" (39, 112, 113).

In 1913 appeared the first extensive discussion of the habitat of the eurypterids in a paper entitled "Early Palaeozoic Delta Deposits of North America" by Professor Grabau, in which he brings forward arguments for the fluviatile habitat of these merostomes in the Ordovicic and Siluric of North America, and he includes a summary of the distribution and occurrence of the eurypterids by myself, reviewing the evidence and coming to the conclusion that the eurypterids were river-living at least during the two periods mentioned. The significance of the occurrences in the Pittsford, Shawangunk, and Bertie are discussed especially.

At the end of the same year Grabau's Principles of Stratigraphy was published. In Chapter XXVIII on the "Bionomic Characteristics of Plants and Animals" and elsewhere in the book the eurypterids are spoken of as fluviatile organisms as indicated by their distribution, faunal associates and mode of occurrence. A single statement taken from this book will show the position which Grabau holds. ". . . . The early remains of fish as of eurypterids are not found in normal marine deposits, but in those which are at least open to the suspicion that they are formed by rivers or at least at the mouths of rivers, while the best preserved remains, and the most abundantly represented in the Palaeozoic, are found in river