58 THE HABITAT OF THE EURYPTERIDA 



occupied land waters chiefly. In the Devonian and Carboniferous 

 periods, in which the eurypterids reached their climax and passed into 

 their decline, and where they seem to have been in their more natural 

 relations, they are associated with land plants, scorpions, insects, 

 fishes, and fresh- water amphibians, which seem to imply a fresh- water 

 habitat. In the light of these facts, the more common inference has 

 been that they were originally marine forms, and became adapted 

 later to brackish and fresh-water conditions. The alternative in- 

 ference is that they were originally denizens of the land waters, and 

 that their remains were occasionally and sometimes quite freely car- 

 ried out to sea by stream waters, and were thus fossilized with marine 

 forms. Their occasional presence in the earlier periods is thus ex- 

 plained, while their seemingly sudden appearance in abundance and 

 in gigantic forms in the closing Silurian, and their prominence in 

 the land-water deposits of the Devonian and Carboniferous finds 

 ready explanation in the fact that these are the first well-preserved 

 fossil-bearing deposits of land waters. In these deposits the euryp- 

 terids often appear without any marine associates, while occasionally 

 there are some marine or at least brackish water forms associated 

 with them, implying either that they lived in brackish or salt water 

 at times, or that their remains were carried out into such waters by 

 the land streams or estuarine currents" (33, 412). 



It is to be noted that European authors have said very little 

 about the habitat of the eurypterids, though there are a few brief 

 references. Geikie is the one exception, for he has a good deal to 

 say about the merostomes and the faunas which occur with them. I 

 shall at this point merely quote a few of these passages, written in 

 the discussion of the Upper Siluric occurrences and of those in the 

 Old Red sandstone. "Vegetable remains, some of which seem to be 

 fucoids, but most of which are probably terrestrial and lycopodiaceous, 

 abound in the Downton sandstone and passage-beds into the Old 

 Red Sandstone. The eurypterid genera continue to occur, together 

 with phyllocarids (Ceratiocaris) and vast numbers of the ostracod 

 Beyrichia (B. Kloedeni). Prevalent shells are Lingula cornea and 

 Platyschisma helicites. The Ludlow fishes are also met with" (74, 

 961). In the discussion of the deposition of the Old Red Sandstone 

 in basins Geikie says: "An interesting confirmation of the view that 

 these basins were isolated is supplied by the occurrence of what is 

 believed to be the oldest lacustrine or fluviatile mo Husk yet known, 

 Amnigenia (Anodonta, Archanodon) jukesii. This shell has been 



