686 , NEW YORK STATE MUSEUM 



Position and localities. Rare in graptolite bed 2 (Tetragraptus zone) ; 

 associated on slabs witli Tetragraptus fruticosus, T. similis, T. 

 pygmaeus and Dichograptus octobrachiatus. The authors of 

 the variety report it from the Upper Skiddaw slates of Outerside in the Lake 

 district of North England. 



Memarhs. I have hesitated for some time to identify my material with 

 the variety from the Skiddaw slates, for the reason that the latter has thus far 



Fig, 83 Didy mograpt us nicholsoni Lap w. t;a.r. planus E. & W. Proximal portion 

 of rhabdosome. Reverse view. Deep kill. x4 



been found in a higher horizon ; but I have failed to find any important dis- 

 tinguishing characters, and the branches and thecae appear to agree with the 

 British types in all details. The somewhat smaller figures for the size of the 

 sicula in our material may be due to an incomplete preservation of the apical 

 end. 'The branches appear to originate in our specimens [see figure 81] very 

 close to the apex of the sicula and diverge from the latter suborally. 



Didymograptus filiformis Tullberg 



Plate li, figures 8-14 



Didymograptus filiformis Tullberg. Geol. Foren. Stockh, Forh. 1880. 5:42, 



pl.2, lig.8-11 

 Didymograptus filiformis Lap worth. Ann. and Mag. Nat. Hist. ser. 5. 1880. 



6:20 

 Did ymograptus filiformis Brogger. Die sil. Etagen 2 and 3. 1882. p.39 

 Didymograptus filiformis Tullberg. Sver. Geol. Und. 1882. Afh. och 



upps. ser.C, no. 50. p. 22 

 Didymograptus filiformis Tornquist. Lunds Univ. Arsskrift, Bd 37, Af 2. 



nr. 5. 1901. pl.3, fig.6-9 

 Didymograptus cf. filiformis Elles & "Wood. Monogr. Brit. Grapt. pt 1. 



Pal. Soe. 1901. p.32, %.20 

 Didymograptus filiformis Euedemann. N. Y. State Paleontol. An. Rep't. 



1902. p.556 



