GRAPTOLITES OF THE HIGHER BEDS 



RANGE AND GEOGRAPHIC DISTRIBUTION 

 In part I of the Graptolites of New York we have drawn the division 

 line between the Lower and Upper Graptolite faunas of New York above 

 the third Deepkill zone (zone with Diplograptus dentatus). The reasons 

 for this proceeding were partly of a practical and parti)' of a theoretical 

 nature ; on one hand we thus obtained an approximately equal division into 

 halves of the subject-matter, and on the other since that zone had been 

 roughly correlated with the Chazy formation, we left all the zones of the 

 Canadian or Paleochamplainic period (the first of the three periods of the 

 ■Champlainic) in association as they are usually found in the field. But we 

 have already emphasized the fact that while the genera of the Axonolipa, 

 which are characteristic of the Lower Graptolite fauna, viz, Dichograptus, 

 Loganograptus, Tetragraptus and Phyllograptus, become extinct with this 

 third zone, the Axonophora, which are characteristic of the Upper Graptolite 

 fauna, appear abruptly in it with their important genera Diplograptus, Glos- 

 sograptus and Climacograptus. The third Deepkill zone is hence truly 

 transitional between the Lower and Upper Graptolite faunas, and if the 

 now prevailing principle, that the division lines should be determined rather 

 by the arrival of new forms than by the extinction of old ones, had been 

 followed, this zone would have been joined to the Upper Graptolite fauna. 

 It partakes, however, in this regard fully of the nature of its correlative, the 

 Chazy formation, which also is more characterized by the advent of genera 

 typical of the later Mohawkian, specially of the Trenton limestone, than by 

 the extinction in it of the older genera of the Canadian era ; and as long as 

 the latter is united into one period with the preceding Beekmantown lime- 

 stone by the New York geologists we are justified in conforming in regard 

 to the corresponding graptolite zone. 



Gurley [1896, p. 304] has provisionally correlated certain small faunas 

 from Mystic (Canada), Kicking Horse Pass (Canadian Rocky mountains) 

 and Dease river (British Columbia) with the Chazy limestone, but since 



