126 NEW YORK STATE MUSEUM 



the actually exposed sections of these limestone strata are very few 

 when compared with the great extent of the beds themselves. It 

 must also be borne in mind, that vast portions of these limestone 

 beds have been removed by erosion during the long post-Siluric 

 time. When we realize that the actual reefs must have been widely 

 scattered in the Niagara sea, and that our sections through these 

 strata are random sections, we need feel no surprise at the unsatis- 

 factory character of these exposures. It must however be added 

 that sections farther east, as at Lockport or other localities, gen- 

 erally show much more of the reef character of the deposit, the 

 corals in these being correspondingly abundant. The upper 

 geodiferous beds of the limestone at Niagara were probably much 

 more fossiliferous than the lower. As before mentioned, the geode 

 cavities most likely are the result of alteration or solution of some 

 fossil body, probably a coral. Though fossils may have been plenti- 

 ful, none of these beds, so far as examined, show the characteristics 

 of true reefs. They have more the aspect of beds of coral sand, 

 on which isolated heads of corals and other organisms grew rather 

 plentifully. 



During the dolomitization of these limestone beds, which was 

 probably brought about by chemical substitution before the con- 

 solidation of the coral sand, many of the fossils which were included 

 in these sands probably suffered alteration and more or less com- 

 plete destruction. Thus it will be seen that even the few organisms 

 which were embedded in these coral sands, did not survive the sub- 

 sequent changes, and thus the barrenness of these great limestone 

 masses appears to be fully accounted for. The fossiliferous char- 

 acter of the upper Clinton limestone, as well as the coarseness of 

 the calcareous fragments of which it is composed, points to a near- 

 ness of this rock to the source of the material; for in the vicinity of 

 the coral and crinoid reefs the food supply for other organisms 

 would be most abundant, and hence these would develop most pro- 

 lifically in such a neighborhood. 



A careful comparative study of the Niagaran deposits of New 

 York and those of the middle states has brought out some im- 

 portant and interesting facts. These may be summed up in the 



