g 2 THE HABITAT OF THE EURYPTERIDA 



nal 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 any- 

 where, 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 typi- 

 cal marine fauna, two species of fish of the type characteristic of the 

 Old Red Sandstone, an ostracod and Orthoceras tenue. The pres- 

 ence of this single cephalopod has been considered by some authors 

 to be so important that they would brand the whole fauna as a modi- 

 fied 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 con- 

 sidered a recognizable faunule — there is not a case, to repeat, in which 

 the faunule, including all of the organisms represented, can be con- 

 sidered either marine or modified marine, that is, brackish or estua- 

 rine. The most constant associates of the eurypterids from the earli- 

 est Siluric on are certain peculiar crustaceans, Ceratiocaris, and the 

 like, which are never found with the molluscs, brachiopods, and trilo- 

 bites 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 euryp- 

 terid formations. In North America, England, Scotland, and on the 

 continent the forerunners of the Old Red Sandstone fishes, now al- 

 most 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, 



