GRAPTOLITES OF NEW YORK, PART 2 53 



graptolites (Graptoloidea), which is the more remarkable when it is remem- 

 bered what an elaborate succession of Upper Siluric graptolite zones lias 

 been worked out in Britain, Scandinavia and Bohemia by means of the 

 Monograptidae. Only the Clinton beds of New York and Maine have 

 yielded a few stragglers and in the Niagaran of the West a single species 

 has been discovered. A lonely Monograptus from Northern Greenland, 

 described by Etheridge [1878, p. 577] as M. convolutus (Hisinger) 

 var. coppingeri, raises the number of true graptolites of the Upper 

 Siluric known from North America to six. It, however, so happens that 

 these few forms are identical or so closely related with typical zone grapto- 

 lites of Europe that they, so to say, illuminate by unexpected flashes of 

 light the equivalency of parts of American Siluric formations with some 

 of the European graptolite zones. 



The Siluric graptolites of the United States are listed with their 

 formations and areal distribution in the preceding synoptic table 2 

 on p.52. 



1 Upper Clinton beds {zone of Monograptus clintonensis C'arruthers) 



The Clinton beds have furnished the following graptolites : 



Dcndrograptus rectus nov. Cactograptus crassus nov. 



Dictyonema pertenue Foerste Monograptus clintonensis ( Hall) 



D. scalariforme Foerste M. priodon Bronn mut. chapmanensis nov. 



Ptilograptus hartnageli sp. nov. Retiolites geinitzianus Barrande var. veno- 



Palaeodictyota clintonensis nov. sus Hall 



P. bella (Hall) mut. recta nov. 



Dictyonema pertenue and scalariforme were first 

 observed by Foerste in the Clinton group of Ohio ; the last has also been 

 found in the horizon of the Clinton iron ore in New York, together with 

 Palaeodictyota clintonensis and P . bella mut. recta, two 

 prenuncial forms of Niagaran species. 



Monograptus clintonensis (Hall) and Retiolites gei- 

 nitzianus Barrande var. venosus Hall, especially the former, occur 

 in great profusion in the higher shales of the Clinton formation, apparently 

 only above the Clinton iron ore bed. Monograptus clintonensis 



