108 THE HABITAT OF THE EURYPTERIDA 



have been of circumscribed area; the Buffalo pool extending from 

 Bertie, Ontario, eastward into Erie County; the Herkimer pool being 

 confined most of the time to the southern part of Herkimer County 

 (See map, fig. 2). In spite of the faunules as a whole having such a 

 restricted distribution, the Eurypterus lacustris of the Buffalo region 

 has been found as far east as Union Springs, Cayuga County, al- 

 though not at intermediate points, and E. remipes, the characteristic 

 form of Herkimer County, has been found to the west at Waterville, 

 town of Westmoreland, Oneida County, and still farther to the west 

 in large numbers at Oriskany, Oneida County, at Cayuga Junction, 

 Cayuga County, and possibly even at Buffalo. Dolichopterus macro- 

 ckirus and Pterygotus cobbi are .common to the two "pools." 



Theories of Origin. A careful determination and a thorough 

 understanding of the conditions under which the Bertie waterlime was 

 deposited are essential in the attempt to determine the habitat of the 

 organisms found in that rock. Because no one has yet given an ex- 

 haustive treatment of all possible conditions of deposition with a final 

 singling out of the true one; and because, moreover, the answer to this 

 question of deposition furnishes one of the most important lines of evi- 

 dence concerning the habitat of the Eurypterida, I shall take up a 

 detailed discussion of the subject. Such a fine-grained, stratified rock 

 might have been deposited in one of the following four ways, and 

 these appear to cover all possibilities: (a) by chemical precipitation; 

 (b) by bacterial precipitation; (c) by the formation of an organic 

 accumulation of calcareous shells or plants, or both; (d) by the 

 accumulation of clastic or fragmental material. 



(a) Chemical origin: That the Bertie waterlime could not have 

 been deposited by chemical precipitation is amply shown by its strati- 

 fication and especially by its composition. A rock which is a chemical 

 precipitate, is more likely to be massive, never showing such fine 

 stratification as is found in the Bertie, for in the process of chemical 

 precipitation there is no arrangement of the material by currents 

 bringing in fresh supplies which vary slightly in color or texture and 

 which when deposited make the separate layers which produce strati- 

 fication, since in precipitation the action is more or less continuous 

 and minute crystals are formed which either entirely make up a rock, 

 or else cement into a compact mass, fine particles of clastic material 

 as is the case around modern coral reefs. The texture of a chemical 

 precipitate would be a finely crystalline one, whereas the material of 

 the Bertie does not conform to this, for a thin section of the water 



