196 THE HABITAT OF THE EUEYPTERIDA 



rest of the eurypterid fauna should have been preserved, (c) If we 

 are to consider that a single fragment of a eurypterid when found in 

 marine strata proves that the eurypterid lived in the sea, then, pro- 

 vided no other proof existed to the contrary, insects, land shells, 

 leaves, logs, spiders, scorpions and other land forms which are often 

 floated or blown out to sea and which are found today thousands of 

 miles from land, and have often been met with in the rocks asso- 

 ciated with marine forms would also be considered as inhabitants of 

 the sea. Since the reasoning given on pp. 93-193 has shown that the 

 most significant and important occurrences of the eurypterids point 

 to a fluviatile habitat, then the single special cases should not be 

 cited as proof to the contrary. It is just as if we were to say that, 

 in spite of the many abundant, well preserved floras of the order 

 Fagales known throughout the world in continental beds from the 

 Cretacic to the present, we were forced to conclude that birch and 

 oak trees have always constituted part of the open marine flora, 

 because in some dredging operations today an oak trunk and a 

 number of birch leaves were hauled up one thousand miles from shore. 

 Specific instances of anomalous occurrences have been cited on p. 

 67, but I shall give one further illustration here to show how little 

 association may mean. 



The Upper Devonic sandstones of Condroz Belgium with an aggre- 

 gate thickness of 22 m., constitute the sandy phase of the Famennian 

 shales of the lower part of the Upper Devonic. They are of interest 

 because of the mixed marine fauna and terrestrial flora found inter- 

 mingled in them; brachiopods, pelecypods, land forms including ferns, 

 and the fish characteristic of the upper Old Red of Scotland are found 

 associated, and the American genus Dictyospongia also occurs in this 

 sandstone. Since at least part of the fauna is marine, and the flora 

 is terrestrial, the eurypterids might be interpreted either as marine 

 or fresh water forms; but inasmuch as only a few fragments have been 

 found, the more rational interpretation would seem to be that the 

 organisms did not live in the sea. This is further borne out by the 

 fact that as the Upper Devonic beds are traced to the south into Ger- 

 many they become pure marine limestones, in which no eurypterids 

 have been found, but traced to the northwest they merge into the 

 Old Red sandstone of England and Scotland which contains euryp- 

 terids and fresh water fishes. The deposits in Belgium, then, mark 

 the meeting-place of the marine and terrestrial waters as the sea 

 encroached from the south upon the Upper Old Red shore, and for 



