GRAPTOLITES OF NEW YORK. PART 1 497 



species, is still entirely composed of Dendroidea and Dichograptidae. The 

 prominent genera are still Tetragraptus, Phyllograptus and Didymograptus, 

 but with new, younger elements. Four of the seven species of Tetragraptus 

 of the preceding zone extend, as stated before, mostly in smaller mutations 

 into this zone, and two other species, Tetragraptus clarkii and 

 pendens, appear as new forms. 



Of the Phyllograpti, P. ilicifolius, which has its acme in the 

 preceding zone, is here rare and disappears ; P. angustifolius becomes 

 more common than before and continues throughout the zone; P. anna, 

 which appeared in the last layer of the pi-eceding zone, is here one of the 

 common and characteristic fossils, but extends also into the lower part of the 

 next zone. P. typus appears for the first time in this zone, becomes 

 extremely common and probably ends with it. It is, hence, apparent that 

 the genus Phyllograptiis culminates in this zone. 



Of the Didymograpti, the horizontal series has dwindled down to one 

 species, D. s i m i 1 i s. The declined series which originated in the preceding 

 zone, continues, but develops very little strength in a specific and individual 

 representation. The dependent series is entirely restricted to this zone and 

 furnishes in D. bifidus and D. nanus most characteristic fossils of 

 the same. The reclined series finally begins here with D. caduceus 

 (gibber ul u s). 



Of the multiramous Dichograptidae, Dichograptus octobrach- 

 i a t u s endures and Goniograptus disappears after developing a last, interesting 

 species in G. geometricus. No more species of Bryograptus are found. 

 The Dendroidea are faintly represented, among them the genus Ptilograptus 

 with two species. With Sigmograptus the coenograptids appear on the scene. 



The characteristic members of this fauna are the Phyllograpti, notably 

 P. typus and P. anna, the dependent or " tuning fork " Didymograpti, 

 D. bifidus and D. nanus; and a horizontal form, D. s i m i 1 i s. 



The principal species were originally reported by Hall from a place " 3 

 miles above the River St Anne." Lapworth recognized this association in 

 collections from the same locality and termed it the St Anne zone or zone 



