GRAPTOLITES OF NEW YORK, PART 1 669 



Description. Pi-imary disk subcircular, relatively large (diameter 5 mm 

 where the rhabdosorae has a length of 6.5 mm), nema short, filiform, very 

 thiu. Sicula inconspicuous, short (1.3 mm) and relatively broad. Branches 

 horizontal, angle of divergence 180°; attaining great length (incomplete 

 specimens measure upward of 40 cm), increasing very gradually in width 

 from .7 mm to 2.4 mm; slightly flexuous. Thecae 9 in 10 mm; short and 

 bi'oad (proportion of length to 

 width, 2:1 in the proximal por- 

 tion and 3:1 in the distal portion), 



attaining a length of 2.2 mm in Fig.62 Dldymograptus extensus Hallsp. Proximal 



° part of rhabdosome. Keverse view. Deep kill. x5.25 



the distal part ; in contact for one 



half of their length in the proximal and two thirds in the distal parts; 

 inclined at an angle of 35° to 40°. Outer and apertural margins sti'aight, the 

 latter nonnal to the axis of the theca (inclined at 130" to the axis of branch). 

 Position and localities. At the Deep kill this species has been found 

 only in graptolite bed 2 (Upper Tetragraptus zone), where it, in association 

 Avith Tetragraptus similis, covers one layer and in others is very 

 common and associated with Dichograptus octobrachiatus, Tetra- 

 g r a p t u s f r u t i c o s u s and Phyllograptus ilicifolius. Hall 



obtained his types from the Quebec group 

 at Point Levis (Tetragraptus zone) ; Lap- 

 Avorth records it also from the zone with 



Fie. 63 Didy mograptus extensus Hall t> u 11 _ „ j. "i." 



»p; Fragment 6f proximal part of branch. Deep PhyllograptuS anna, Citing aS 

 kill. X5.25 . . 



locality " 3 miles above St Anne " ; and 

 Ami lists D. extensus from several localities in the neisrhborhood of 

 Levis. In Great Britain it has been recognized in the Middle Skiddaw 

 slates of the Lake district ; in the St David's district and tlie Lleyn 

 peninsula of Wales (Hick's Lower Areuig) ; in Shropshire ; and in the 

 Ballantrae district in Scotland. Brogger records it from the Pliyllograptus 

 shale of the Christiania region ; Tornquist found it in the zone of 

 Isograptus gibber ul us (lowest zone of his Phyllo-Tetragraptus 

 beds) of Scania ; and Freeh mentions it also from the Hunneberg in 



