1 124 PRINCIPLES OF STRATIGRAPHY 



Calciferous replaced by Beekmantown. 



Birdseye replaced by Lowville. 



Waterlime (of Buffalo) replaced by Bertie. 



Coralline replaced by Cobleskill. 



Waterlimes (of the Hudson) replaced by Rondout & Rosendale 



Tentaculite limestone replaced by Manlius. 



Lower Pentamerus replaced by Coeymans. 



Delthyris shaly replaced by New Scotland. 



Upper Pentamerus replaced by Becraft. 



Upper Shaly replaced by Port Ewen. 



Cauda-Galli replaced by Esopus. 



Cornif erous replaced by Onondaga 



As the Palaeozoic formations of other districts of North America 

 were studied, it was found that the correspondence between them 

 and the New York formations was not as close as could have been 

 hoped. Not only did the lithic character of the strata change 

 when traced away from the type locality, but the superposition did 

 not, in many cases, correspond, some formations being absent alto- 

 gether while others were found to be united in a single unit, often 

 of slight thickness. Even the fossils, which had gradually come to 

 be looked upon as the surest indicators of position in the geologic 

 scale, appeared in horizons not known to contain them in New York. 

 Thus the chain-coral Halysites was universally thought to be char- 

 acteristic of the Lower Siluric (Niagaran) age, until it was dis- 

 covered that this coral also occurred in the Ordovicic, in some of 

 the localities west of New York, and in the Anticosti region, while 

 in eastern New York it was found in an Upper Siluric horizon, the 

 Cobleskill, which is stratigraphically many hundred feet above the 

 Niagaran beds. In like manner Tropidolcptus carinatus and some 

 of its associates, believed formerly to be restricted to the Hamilton 

 (]\Iid-Devonic) formation, were found in south central New York 

 to occur in the Ithaca (Portage) beds and, again, in the Chemung 

 (Upper Devonic). 



Recurrent faunas have also been described from the Mississipic. 

 Weller (53) found Devonic elements in the Kinderhook fauna, and 

 Williams and others have described such recurrence of Devonic 

 elements in the Spergen and other Mississippic beds of central 

 North America. Ulrich (49 -.jpd) has noted the occurrence of the 

 trilobite Triartlinis becki in the Fulton shale, and in the Southgate 

 beds 150 feet above it. 



Chronological Equivalency. Contemporaneous and H oniotaxial 

 Formations. Chronological equivalency as one of the fundamental 

 data of geologic history has repeatedly been assailed by eminent 

 scientists. Huxley, indeed, went so far as to question the possi- 



