REPORT OF THE STATE PALEONTOLOGIST 1902 897 



the more actively moving groups of animals, such as snails and 

 cephalopods. A sea answering all the above conditions could 

 not be an open extensive body of water, like an ocean, but must 

 rather have been more of the nature of a great swamp, with its 

 open lagoons and connecting passages. This condition would in 

 a measure account for the deposition of pyrite in disconnected 

 but not widely separated areas. The animals in the iron-bearing 

 lagoons would feel the dwarfing effect; those outside would be 

 free from such conditions; and occasionally a normal individual 

 might readily drift in among the dwarf faunas. 



The fossils in this collection represent three specific areas, 

 one on Canandaigua lake, Ontario co., one about Livonia, Liv- 

 ingston co., and one near Moscow, Genesee co. Of these, the 

 first two seem to have been more isolated, the last has frequent 

 larger forms which have drifted into it. In all the areas, how- 

 ever, the degree of dwarfing is practically the same. 



In considering the relative time required to produce this 

 dwarf fauna, or to deposit the pyrite layer, it is clear that 

 the greatest dwarfing would be accomplished by the chemical 

 action on the embryos; and it is equally evident that the life 

 of several generations would be necessary to reduce a species 

 to one fifteenth of its normal size. One might expect, that in 

 the lowest parts of this deposit, the first generations which had 

 lived in the iron water would be larger, and that those above 

 would be successively smaller, as they had been exposed longer 

 to the unfavorable conditions. This is not, however, the case. 

 The animals from the bottom of the pyrite are of the same size 

 as those from the upper part. There seemed to be fewer indi- 

 viduals in the top than in the bottom part of the pyrite, but 

 fossils were distributed all the way through. Hence it appears 

 that the first embryos to "be affected by the iron are as much af- 

 fected as were the following generations which were descended 

 from those dwarfs. 1 By the time these first dwarfs bred, they 

 seem to have accustomed themselves to the abnormal environ- 

 ment, so that their progeny grew as large as the parents. 



1 This is a proposition which requires verification; but at present I know of 

 no experiment which has been carried through several generations and observa- 

 tion taken in regard to the growth under such unfavorable circumstances. 



