Fig. 52 Tetragraptus quadri- 



GRAPTOLITES OF NEW YORK, PART 1 647 



district in south Scotland. Brogger records it from the region of Christiania, 

 the Swedish authors from Dalecarlia and the Teti'agraptus 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. 



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

 distinguished from Gi-raptolithus bryonoides by its straight and 

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

 fossil." Indeed, the geometric regularity 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 downward direction of the 

 thecae, with rare exceptions only the dorsal or 



ventral side is exhibited, and the profile view brancheaiarg^ed.^Deepkiu.^'S.a"^ °* 

 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. amii, evi- 

 dently on account of its broader and correspondingly heavier branches. 



Tetragraptus amii Lapworth ms, (EUes &, Wood em.) 



Plate 11, figures 5-7 



Graptolithns bryonoides Hall (pars). Geol. Sur. Can. Grapt. Quebec Group. 



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

 Tetragraptus amii Elles & Wood. Monogr. Brit. Grapt. 1902. ptl. Pal. See. 



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



