GRAPTOLITES OF NEW YORK, PART 1 647 



district iu south Scotland. Brogger uecords it from the region of Christiania, 

 the Swedish authors from Dalecarlia and the Tetragraptus zone in Scania. 

 Barrois cites it as being rare in the graptolite schists at Cabrieres in 

 the Languedoc, and McCoy reports it from the shales of Victoria, 

 Australia. 



Reitiarhs. Hall said of this species, that it, "when entire, is readily 

 distinguished from Graptolithus bryonoides by its straight and 

 more slender branches, and by the general aspect and expression of the 

 fossil." Indeed, the geometric ]-egularity of the disposition of the branches 

 in the compressed material, combined with their slenderness, will readily serve 

 as a distinctive character, even where the various species of Tetragraptus are 

 promiscuously mixed, as in graptolite bed 2. On 

 account of the original horizontal position of the 



branches and the do-wnw^ard direction of the ^ _ ^-^^^^^^^^ 



thecae, with rare exceptions only the dorsal or -^ ^„ ^ 



' J- ^ Fig-. 53 Tetragraptus quadri- 



ventral side is exhibited, and the profile view brancheailrged.'"Diep'kiii.^°^.2'° °* 



can be observed only when, as in the original of 



figure 3, the branches were, during entombment, turned to one side. Also 



on account of this position of the rhabdosome the sicula is, in the shale, 



always embedded in its natural vertical position and therefore only seen in 



sections. 



The horizontal and rigid position of the branches is evidently largely due 

 to the character of the dorsal perisarcal wall of the coenosarcal canal, 

 which in the flattened specimens alone projects bodily and appears like a solid 

 axis. The same feature is found still more emphasized in T . a m i i , evi- 

 dently on account of its broader and correspondingly heavier branches. 



Tetragraptus amii Lap worth ms. (EUes &, Wood em.) 



Plate 11, figures 5-7 



Graptolithus bryonoides Hall (pars). Geol. Sur. Can. G-rapt. Quebec Group. 



Figures and Descriptions, decade 1. 1865. p.84, pi. 4, fig.9, 10 

 Tetragraptus amii EUes & Wood. Monogr. Brit. Grapt. 1902. ptl. Pal. Soc. 



p.60, pi. 5, fig.4a-c 



