REPORT OF THE STATE PALEONTOLOGIST 1902 955 



The fact, that the Upper Cambric Dictyonema and the Lower 

 Siluric Phyllograptus zones have apparently been united by 

 Dale in his horizon F, demonstrates the lithologic identity of 

 the beds, also observed by the writer and suggests, as stated 

 before, the continuation of the same physical conditions from the 

 Upper Cambric into the Lower Siluric time. 



Possible subzones of the Dictyonema horizon 



Whether the Dictyonema bed of New York will ever admit 

 a further division into subzones, we are at present unable to sur- 

 mise. In Norway Brogger has found that the mut. norvegica 

 lies a little higher than the typical Dictyonema flabelli- 

 forme. In Sweden, Linnarsson, in 1871, had already 

 discerned a zone with Clonograptus tenellus Linn., 

 which was at first thought to lie below the Dictyonema 

 flabelliforme zone, and to be associated with the Cam- 

 bric trilobite Sphaerophthalmus alatus. Moberg 1 

 has, however, shown that this form lies above Dictyonema 

 flabelliforme, and that the latter species occurs in 

 layers immediately adjoining those with Sphaerophthal- 

 mus alatus. 



Not very long ago Anton Nilsson and Axel Tellander 2 demon- 

 strated that also in southern Sweden (near Fogelsang, Lund 

 sheet) several zones can be discerned, namely, in descending 

 order : 



Zone with Dictyograptus norvegicus Kjerulf and 

 Bryograptus kjerulfi Lapw. 



Zone with Clonograptus cf. flexilis Hall. 



Zone with Dictyograptus flabelliformis Eichw. 

 forma typica. 



Their observations verify Brogger's statement of the occur- 

 renee of Dictyonema flabelliforme var. norve- 

 g i c u in and of Bryograptus kjerulfi above the 

 typical Dictyonema flabelliforme. 



Matthew's results did not suggest to him a possible separa- 

 tion into a Clonograptus and Dictyonema zone. At Schaghti- 

 coke the two occur separated, but it is impossible to say posi- 



1 Sver. Geol. Unders. Afhandl. och upps. ser. C. no. 125. 1892. p. 1-16 

 2 Geol. Foren. Ftfrhandl. no. 201. 1900. 22:421-26. 



