498 NEW YORK STATE MUSEUM 



with Phyllograptus anna. Gurley [1896] records the occurrence of 

 D i d y m o g r a p t u 8 b i f i d u s and Phyllograptus anna in the 

 graptolite shale of Nevada. 



In Great Britain Lapworth records a similar association from the Ballan- 

 trae rocks in south Scotland. In the Skiddaw slates the characteristic species 

 of the zone, specially Didy mograp tu s bifidus, Phyllograptus 

 t y p u 8 and Phyllograptus anna, are found in the upper Tetragraptus 

 subzone which overlies the Dichograptus zone. In Scania the zone with 

 Phyllograptus cf. typus and D i d y ni o g r a p t u s cf . bifidus forms, 

 according to Tullberg, the highest part of the lower graptolite shale and 

 overlies the Orthoceras limestone. But as this is also reported to contain 

 Climacograptus and Cryptograptus, which here do not appear till the next 

 zone, this Scanian and the Deep kill zone can not be exactly parallelized ; and 

 it is to be assumed that the typical St Anne fauna lies a little deeper and is 

 homotaxial with a part or the whole of the Orthoceras limestone itself. 



In Bohemia Didymograptus bifidus occurs in D dlr [Perner]; 

 and in France its occurrence and that of Rouvilligraptus richard- 

 soni, another St Anne form, indicate the presence of the St Anne zone 

 in the graptolite shale of Cabri^res. Finally, T. S. Hall [1893] recognized 

 the zone of Didymograptus bifidus in the auriferous shales of 

 Victoria, Australia. 



It is hence, with our present evidence, to be inferred that this zone in all 

 lower graptolite beds of the world is directly successive to and also coextensive 

 with the preceding Tetragraptus zone. 



d Zone with Diplograptus dentatus and Climacograptus? antennarius. 

 This zone is represented at the Deep kill by graptolite beds 6 and 7, which 

 are separated by an interval of several hundred feet of nonexposure from the 

 zone with Didymograptus bifidus. The writer's supposition [1902] 

 that this interruption hides a transitional zone, of similar composition as 

 the one, just mentioned, in Scania, with Didymograptiis bifidus, 

 Phyllograptus typus, intermingled with the graptolites of the zone 

 of Diplograptus dentatus, has to some extent been verified by a 

 fauna found at Mt Moreno \siee note below]. 



