522 A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



the problem from the side of the sediments, attempting to determine 

 their source and mode of deposition. 



Taking the organisms first, we find that the specimens, though well 

 preserved, appear to represent chiefly exoskeletons. Clarke and Euede- 

 mann give it as their opinion that "probably the majority of the remains 

 found are the cast exuviae from the frequent moltings of growing indi- 

 viduals." Secondly, there is a remarkable absence of other organisms 

 which could, have served as food for these creatures. True, remains of 

 some plants, apparently aquatic, of Ceratiocarids and of a few entire 

 gastropod shells are found. There seem to be, however, no indications 

 of organic remains which could have served these Arachnids for food, 

 nor does the water-lime anywhere show evidence of broken shells or skele- 

 tons other than the Eurypterids. In texture and presumably in origin, 

 the water-lime is exactly the same whether Eurypterids abound or are 

 wholly absent, as in the Eosendale section. Unless these creatures lived 

 on shell-less organisms which have left no remains, this could not have 

 been their habitat, for we can hardly assume that they were purely can- 

 nibalistic. That the "pools" were almost if not quite lifeless is shown 

 by the scantiness of other than Eurypterid and Ceratiocarid remains. In 

 the Buffalo pool, besides the plant remains, occurs an occasional Lingula 

 or Leperditia, which probably were washed in from the open sea, as was 

 perhaps the case with the four examples of dead orthoceras shells found. 

 The only fossil besides the Eurypterids represented by a number of speci- 

 mens are shells of Hercynella buffaloensis O'Connell* (identified as 

 Discina grandis in the collections), which is regarded as a pulmonate 

 gastropod and may have belonged to the river fauna, though it, too, may 

 have been washed in from the sea. The Herkimer pool has furnished 

 evidence of the proximity of the land in the occurrence of a scorpion, the 

 Proscorpius osborni Whitfield with the Eurypterids. 



But by far the most marked faunal peculiarity of the Bertie is the 

 separation into two distinct pools, as noted above. As shown by the quo- 

 tation from Clarke and Euedemann given in Miss O'ConnelPs summary, 

 the faunas of these two pools are distinct, having only two of the rarer 

 forms in common. How can such a segregation of species be accounted 

 for? Clarke and Euedemann consider that the difference is due not to 

 differences in horizon of the two series, but has rather a geographic basis, 

 bringing about isolation of these faunas. How can we conceive of such 

 segregation on a sea-border or in lagoons open to the sea? It must be 

 remembered that this is not an ordinary case of local marine provinces, 

 for first of all the entire order of the Eurypterids is virtually restricted 



* Manuscript in preparation by Miss O'Connell. 



