DISTRIBUTION AND OCCURRENCE OF EURVPTERlDS 525 



Salina period had prepared the material for the rivers to sweep into the 

 basins of deposition. Some of this material was swept into the Salina 

 basin during the intervals of salt deposition and so formed the dividing 

 dolomitic bands. But the bulk of the lime sand and lime mud produced 

 by mechanical disintegration and erosion of the old Niagaran limestones 

 of the Siluric land was utilized to build the fine-bedded Upper Siluric 

 or Monroan strata, of which the water-limes are the most marked ex- 

 amples. If more lime mud and sand is furnished to a river than it can 

 take into solution, the surplus must be carried away as mechanical 

 detritus and deposited where the river currents are checked. If this is 

 in the sea, well stratified calcilutytes inclosing marine organisms will be 

 formed; if in a playa lake, finely stratified deposits free from marine 

 organisms result. This latter I believe to have been the conditions 

 under which the Bertie water-lime was deposited. A series of shallow 

 basins above sealevel, but near the coast, were flooded by the waters of 

 the rivers, which brought large quantities of fine lime mud. With this 

 lime mud were brought at certain times the cast-off exoskeletons of the 

 Eurypterids and Ceratiocarids which inhabited the upper reaches of the 

 rivers. Near the margins of these basins grew reedlike vegetation, the 

 remains of which are often found in these deposits. Finally, pulmonate 

 gastropods (Hercynella), living among these reeds, were occasionally 

 entombed. Once or twice the sea may have broken into these basins, 

 washing with it a couple of dead orthoceras shells and the shells of a few 

 Lingulas and perhaps some ostracods. Even this is doubtful, since the 

 Orthoceras and Lingula shells may have weathered out from the older 

 limestones of the land and become transported into the Buffalo basin, 

 where they were found. The same is true of the Leperditias, though 

 these may actually have inhabited the waters of these basins. In any 

 case, the presence of these few marine organisms is readily explained 

 and offers no barrier to the general acceptance of the theory of origin 

 here outlined. This seems to accord best with all the known facts, 

 whereas the commonly accepted theory of a marine origin of these sedi- 

 ments and faunas meets with insuperable difficulties and requires special 

 hypotheses at every step to bolster it up. 



The composition of the Bertie water-lime is in harmony with the idea 

 of its origin from the Lockport and Guelph dolomites, containing 20.35 

 per cent of magnesium carbonate and 42.75 per cent of calcium car- 

 bonate. 122 The presence of 11.48 per cent of silica and 17.5 per cent 

 of alumina also indicates that the material is land derived, that there is 



122 From analyses of Buffalo water-lime made for Lewis J. Bennet, 



