84 



of the remains, which indicate a considerable amount ol 

 wave action, as well as by the grains of sand which occur 

 in the rock. 



While the crinoids flourished in this spot, and while similar 

 conditions probably existed elsewhere, there came, perhaps 

 from Ohio and the south-west, representatives of the great 

 Placoderms which had ruled for many generations in those 

 waters. These fishes seem to have found the area where the 

 crinoids flourished, an exceptionally good feeding ground if 

 w^e are to judge from the frequency of their remains in the 

 rock. Living among the crinoids was a vast number of 

 marine worms, the record of whose existence is now found 

 in the "Conodonts," so plentiful in the rock. These bodies, 

 as already noted, probably represent the oesophageal teeth 

 of animals similar to our modern Annelida and Gephyrea. 



As the subsidence continued, and the water became purer 

 over larger areas, there began the deposition of the countless 

 millions of shells of the minute pteropod Styliolina £ssurella, 

 which as noted above, in many places completely make up 

 the Stvliolina limestone. The conditions which favored the 

 deposition of this limestone, were quite uniform over the 

 greater portion of what is now Western New York. The 

 character of the rock indicates that it was deposited at a 

 distance from shore, where comparatively little sediment 

 was carried, so that, as on the death of the pelagic animals, 

 the vshells slowlv sank down from the surface, the\' accumu- 

 lated by the millions on the ocean floor and formed a lime- 

 stone bed of great purity. The accumulation of this 

 inconceivably vast number of minute shells must have been 

 a process of extreme slowness, even if we suppose that large 

 numbers of the animals were carried to this region b}' 

 favorable currents. It must be noted, however, that in 

 man}' localities this bed contains a considerable amount of 

 foreign matter, showing that some deposition of detrital 

 material was going on. 



