Page:The Habitat of the Eurypterida.djvu/98

 chitin and specimens can be removed from the rock almost entire; the surface sculpture and internal structure are as clearly visible as in a Limulus buried in the sand but yesterday. We have here, if anywhere, a representation of the normal habitat of the Eurypterida, and likewise the normal faunal associates. The analysis of this fauna shows that besides the eurypterids there are a number of crustacea which are commonly found with the merostomes, but never in a typical marine fauna, two species of fish of the type characteristic of the Old Red Sandstone, an ostracod and Orthoceras tenue. The presence of this single cephalopod has been considered by some authors to be so important that they would brand the whole fauna as a modified marine one, because of it; and yet the startling and commonly neglected fact is that this thin shelled Orthoceras is most evidently out of place, for while the eurypterids are so marvellously preserved, this one rare cephalopod is worn, macerated, and flattened into a tenuous, carbonaceous film, and thus there is no doubt that it was transported from its normal habitat and came probably as a dead shell into the region where the eurypterids were living. Its presence is truly of great importance as being the very exception which proves the rule that the eurypterids were not normally marine.

A glance at the components of the fourteen faunas listed shows that there is not a single case in which several species of eurypterids are found in a fair state of preservation in such numbers as to be considered a recognizable faunule—there is not a case, to repeat, in which the faunule, including all of the organisms represented, can be considered either marine or modified marine, that is, brackish or estuarine. The most constant associates of the eurypterids from the earliest Siluric on are certain peculiar crustaceans, Ceratiocaris, and the like, which are never found with the molluscs, brachiopods, and trilobites which are characteristic of marine faunas. The oldest scorpion known comes from beds carrying eurypterids, similarly the earliest fluviatile pelecypod and the first myriopods were also found in eurypterid formations. In North America, England, Scotland, and on the continent the forerunners of the Old Red Sandstone fishes, now almost universally recognized to be fluviatile, are found in the Siluric with the eurypterids, crustacea and spores of land plants, but not in the beds carrying typical marine fossils.

In the Bertie waterlime, which is second only to the waterlime of Oesel in importance, a large eurypterid fauna is found with abundant Ceratiocaris, two species of pulmonate gastropods, a problematic plant,