GRAPTOLITES OF NEW YORK, PART 2 2C>7 



Thamnograptus typus Nicholson. Mon. Brit. Grapt. 1872. p. 131, fig. 71 



Thamnograptus barrandi Gurley. Jour. Geol. 1896. 4 : 88 



T h a m n o g r a p tus t y p u s and T li . b a r r a n d i i Lapworth. Cat. West. Scott. Foss. 



1S76. p. 7 ; pi. 4, fig. 95, 96 

 Thamnograptus typus? Lapworth. Belfast Nat. Field Club Rep't & Proc. 1877. 



v. 1, Apx. p. 143 ; pi. 7, fig. 16 

 Thamnograptus barrandii Lapworth. Roy. Soc. Can. Trans. Sec. 4. 1886. p. 178 

 ? Thamnograptus typus T. S. Hall. Australasian Ass'n Adv. Sci. 1893. p.i of 



sep. copy 

 Thamnograptus typus Clark. Geol. Mag. 1902. Ser. 4, 9 : 498 



Description. Rhabdosome large (distal portion, representing obviously 

 but a small part of the whole stock, measuring 1 10+ mm), consisting of a 

 straight or slightly zigzagged main stipe and numerous orders of branches, 

 those of the first order being arranged in alternating order, directed sub- 

 horizontally and 3 mm— 5 mm apart ; those of the later ones arranged on 

 one side of the mother branch, and but 1.5 mm apart. The complete 

 rhabdosome is surrounded by a dense mass of hairlike branches. The 

 main stipe and the older branches attain a width of 1.6 mm, the distal 

 branches but .1 mm. The main stipe and the branches of the first order 

 are composed of very, slender, tubular, frequently curved thecae which over- 

 lap nearly one half their length, have but slightly projecting apertures with a 

 small apertural mucro and number five to six in the space of 10 mm. From 

 the proximity of their apertures proceed the extremely delicate branches 

 of the higher orders, whose structure has not been made out. Sicula not 

 observed. 



Position and localities. Hall's types were collected in the Normanskill 

 shale at Kenwood near Albany. Other specimens have been obtained in 

 the same horizon at Glenmont near Albany, on Mount Moreno and at 

 Stockport ("Nemagrapsus capillaris "). This species is, therefore, 

 while nowhere common, apparently a constant element of the Normanskill 

 fauna. Lapworth has also recognized it in the Glenkiln shales of Scotland 

 and in Ireland. The T. typus of Victoria, Australia is associated with 

 forms of the Deepkill shales and doubtful. 



