GKAPTOLITES OF NEW YORK, PART 1 499 



This third Deep kill zone is characterized by the suppi-ession of the 

 Dichograptidae and the unheralded appearance of the axonophorous Diplo- 

 graptidae, with the genera Diplograptus, Glossograptus, Trigonograptus, 

 Climacograptus and Retiograptus, which now dominate till the end of the 

 Lower Siluric. Accordingly, between this and the underlying zone, there 

 has taken place a profound change, indeed the most profound change to be 

 met with between the successive graptolite faunas; for a new subclass, the 

 Axonophora, built on an entirely new plan, have taken possession of the field, 

 and the Dichograptidae, hitherto holding sway in the wide areas occupied by 

 the graptolites, persist only in a few stragglers. 



Note. Transitional subzone. Tlie fortunate discovery of a Phyllograptus in the 

 shales of the Ashhill quarry at Mt Moreno near Hudson, by Prof. A. W. Grabau, has led 

 to the finding there of a fauna which is a blending of the typical forms of the zone with 

 Diplograptus dentatus with some species of the preceding zone. It, therefore, 

 appears to happily fill, to a great extent, the gap in the continuity of the graptolite 

 horizons, caused by the interruption of the outcrops between graptolite beds 5 

 and 6 of the Deep kill section (zones with Didymograptus bifidus aad 

 Diplograptus dentatus).' 



The lithologic character of the beds at the Ashhill quarry is strikingly similar to that 

 of the Deep kill beds, the bands of black graptolite shales being also intercalated in 

 thicker masses of greenish, silicious shales.' 



The Ashhill quarry has furnished the following forms : 



D. cuspidatus sp. nov rr 



D. spinosus sp. nov r 



Dendrograptus sp r 



Ptilograptus plumosus Hall c 



Goniograptus perflexilis sp. nov, mui . . rr 



Tetragraptus quadribrachiatus Hall .... rr 



T. taraxacum sp. nov rr 



T. pygtnaeus sp. nov r 



Didymograptus forcipiformis sp. nov. . c 



D. filiformis Tullherg r 



D. gracilis Tomquist r 



Phyllograptus angustifolius Hall c 



Diplograptus dentatus Brong cc 



D. laxus sp. nov c 



Climacograptus pungens sp. nov cc 



Glossograptus hystrix sp. nov r 



Trigonograptus ensiformis Hall , . rr 



Retiograptus tentaculatus Hall r 



^See N. Y. State Paleontol. An. Rep't 1901, pi. 3, facing p. 546. 



2 As at Mt Moreno these Lower Champlainio graptolite shales are exposed in close proximity to 

 the Normanskill shales of Trenton age, this locality will be noticed in greater detail in a later 

 publication in the report of the state paleontologist. 



