Lower Silurian.} PALAEONTOLOGY OF VICTORIA. IGraptolitcs. 



Plate I., Fig. 6. 

 DIPLOGRAPSUS PRISTIS (His. sp.). 



Description. — Straight, simple, about 1 to 2 inches long, and 1 line wide, 

 gradually tapering to the base ; central axis capillary ; the dissepiments diverging 

 from it at an acute angle, their upper and lower margins parallel, forming narrow 

 cylindrical tubes, when uncompressed, with the opening simply truncate at the outer 

 end ; when compres.sed the walls of the cells form parallel lines, very oblique to the 

 axis, producing denticles at the edge, with a long straight lower, and a very short 

 concave upper, margin, 6 in the space of 2 lines. 



Reference. — Prionotus pristis (His.), Leth. Suec, t. 35, fig. 5. Var. B. 

 (Hall), Pal. N. Y., t. 72, fig. 1, r, s. 



The probably distinct species var. B. accompanies the above in 

 the Utica slate of New York, and I have foimd it also rarely at 

 Lockerby and in Victoria ; it seems distinct from the true pristis 

 by its broader triangular teeth, slightly mucronate at the tip, and 

 cells much less oblique to the axis ; it is more strongly and broadly 

 toothed than the D. mucronatus. 



Very common in the whitish decomposing flags of (B'' 67) 

 section 24, parish of Bulla ; B'' 66 ; B" 62 ; black flags of ranges 

 N. of Camp Lancefield (B^ 29) ; in slates (W.L.S. 1) of section 16, 

 parish of DarriTvill, Sutherland's Creek. 



Explanation of Figures. 

 Plate I. — Fig. 6, specimen, natural size (the ink has encroached on the figure, reducing It 

 too narrow). Fig. 6a, portion magnified. 



Plate I., Fig. 7. 



DIPLOGRAPSUS RECTANGULARIS (McCoy). 



Description. — Straight, simple, usually from 1 to 1^ inches long, about 1 line 

 wide, gradually tapering to the base, which is a fine simple point; axis fine, 

 capillary ; cells perfectly at right angles to the axis, forming square denticles to the 

 margin, distinctly separated by rather wide parallel-sided notches, reaching § of the 

 way to the axis ; 5 in the space of 2 lines. 



References. — (McCoy), Annals Nat. His., 2nd s., vol. vi., p. 271 ; Brit. Pal. 

 Fos., pi. 1 B, fig. 8. 



This species is more distinct and constant m its characters than 

 most of the allied forms. In general appearance it approaches the 



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