32 NEW YORK STATE MUSEUM 



The same can be said of another at present also isolated fauna that has 

 been found by the writer at the power house below Mechanicville on the 

 right bank of the Hudson river [see Bui. 42, 1901, p.519]. It consists of a 

 large number of brachiopods, mollusks and crustaceans partly denoting 

 Utica, partly Trenton age, and the following graptolites : 



Corynoides curtus var. comma nov. Glossograptus quadrimucronatus var. ap- 



Diplograptus foliaceus Murchison proximatus nov. 



Climacograptus caudatus 



Climacograptus caudatus is restricted in Europe to the 

 zone of Dicranograptus clingani, which corresponds to the Magog shale 

 and lies between the zones of Nemagraptus gracilis (Xormanskill shale) 

 and Pleurograptus linearis (Utica shale). It has also been found in the 

 Magog shale itself. Its occurrence in the Mechanicville shale together with 

 a mutation that is restricted to this bed (Corynoides curtus var. 

 c o m m a ) indicates a transitional subzone lying somewhere near the 

 boundary of the Magog and Utica shales. We will for the present desig- 

 nate it as the subzone of the two mentioned forms. 



The Climacograptus caudatus has also been found by 

 the writer in shales dredged from the Hudson river at the city of Troy. 

 The location of this latter shale indicates its stratigraphic proximity to the 

 shales with Diplograptus amplexicaulis, our principal representative of the 

 Magog shale. 



In Great Britain Lapworth [1880, p. 198] has distinguished a zone of 

 Dicranograptus clingani Carruthcrs which follows that oi Nemagraptus 

 gracilis. It is in its turn succeeded by the zone of Pleurograptus linearis 

 Carruthers, which roughly corresponds to our Utica shale [see postea\. By 

 its relative stratigraphic position the Magog shale may, therefore, be 

 expected to correspond to the zone of Dicranograptus clingani Carruthers. 

 Although no complete fossil lists of the British zones, that would admit 

 positive correlation are at hand, the presence, in the Magog shale, ot such a 

 form as Climacograptus caudatus that in Great Britain is restricted 

 to this zone, leaves little doubt of their homotaxy. 



