BUFFALO SOCIETY OF NATURAL SCIENCES 99 



of the sea. It is often argued that such alternations of sandstones 

 and shales as we see in this series indicate near-shore oscillatory 

 conditions, the shales marking a slight advance of the sea and of fine 

 deposition, the sands marking a retreat and the seaward advance of 

 continental elastics. In the present instance it is difficult to explain 

 the presence of eurypterids as marine organisms if we account for the 

 lithological variation in the customary manner, for it is in the sand- 

 stones which mark the dominance of terrigenous sedimentation that 

 the eurypterids are more abundant, while they are scarce in the 

 shales which accompany the advance of the sea. If they were living 

 along shore they should be abundant in the shales. The reply may 

 be made that the eurypterids at that time preferred the sandy facies 

 only and that the occurrence of dead individuals or shed exoskeletons 

 in the muds was fortuitous. A phenomenon can hardly be called 

 fortuitous which occurs again and again in response to a given set of 

 conditions. Furthermore, if the eurypterids did live in the sandy 

 facies then there is no reason why their remains should not have been 

 preserved, for it is a mistake to believe that such exoskeletons would 

 be destroyed by the waves, except perhaps on a shingly beach, a 

 facies with which we are not here concerned. A short distance out 

 to sea eurypterid remains would quickly be buried, the hollow case 

 being soon filled by infiltrating sand. Anyone familiar with the 

 occurrence of Limulus exoskeletons on sandy shores knows that they 

 are easily filled by and buried in the sand and that they are pre- 

 served in to to, not broken to pieces. Thus we cannot account for 

 the occurrences of the eurypterids on the assumption that they are 

 marine organisms. In the Normanskill . beds not a single entire 

 specimen has been found, the whole fauna being made up mostly of 

 carapaces with some separated abdominal segments. In the Schenec- 

 tady sandstones the conditions are the same, but in the shales the 

 preservation is better. 



The evidence clearly militates against a marine habitat for the 

 eurypterids in these two regions and the hypothesis of a fluviatile 

 origin while not yet very strongly supported at least accounts for the 

 observed facts. If the eurypterids were living in the rivers in Middle 

 and Upper Ordovicic time, then it is to be expected that their remains 

 would be carried out to sea. In rivers of moderate gradient it is not 

 so likely that an abundance of remains of fluviatile organisms will 

 be washed seaward, for they may be entirely broken up during trans- 

 portation, or they may be caught in hollows along the banks, or even 



