Lower Silurian.'] PALiEONTOLOGY OF VICTORIA. IGraptolites. 



branching into 2 nearly straight branches, a little more or less than 1 line long, 

 each of these dividing- into 2 (or occasionally 3 b}^ a 4th furcation, about a line distant 

 from the preceding one) nearly straight branches; the vinculum branches as far as a 

 little beyond the 3rd or 4th bifurcation, about J of a line wide; beyond this the 

 simple branches are several inches in length [and when compressed are slightl}' more 

 than a line wide, including the point of the cell denticles which are about 

 18 in the space of an inch] ; other s])ecimens have as many as 28 in an inch, 

 and are onlj' | of a line wide : the cell denticles are sometimes on one side, sometimes 

 on the other, only indenting the edge after the 3rd bifurcation from the centre; 

 they project rather less than half the width of the branch, are acute, the upper edge 

 moderately concave and the lower margin moderatel}' oblique, arched and reaching 

 the back margin opposite the point of the next but one lower denticle ; the width of 

 the branch from back to point of denticle about equal to li of the spaces between 

 the denticles. The middle portion, before the 3rd or 4th or final branching, marked 

 with an impressed central line representing the back tube of the branches. 

 Reference. — (Hall), Can. Org. Rem., dec. 2, p. 100, t. 9 and 11. 



I have enclosed in brackets [ ] the only characters in which the 

 var. Australis differs from the orchuary Canadian types as made 

 known by Hall, namely, a greater width (in one compressed 

 specimen, B* 78) of the branches, and a smaller number of denticles 

 in an inch by 10, according to Hall's description, but only of one 

 according to his figures. The large specimen figured B" 78 has 

 8 branches on one side of the vinculum and 10 on the other, as in 

 many of the Canadian specimens. As Professor Hall considers the 

 disposition of the branches the chief diagnostic character of his 

 species, G. Logani, I refer the Australian form which is perfectly 

 identical in this respect to it, indicating the two differences in 

 measurement of some of the specimens, and affixing a geographical 

 name to the variety for separate reference ; in the same slates, 

 however, at Castlemaine, are other specimens in which the branches 

 are only | of a hue wide, and the denticles reach 27 or 28 in an 

 inch, agreeing thus in all respects with the Canachan ones. Many 

 specimens show only what Hall terms the outer side or non-celluli- 

 ferous edge, so that the vinculum and branches, to an inch or more, 

 show only as equal filiform rugged lines of the width of the tubular 

 marginal canal which then occupies the middle, but which appears 

 on the entire edge of denticulate specimens. 



Both the var. Australis and the typical forms finely developed 

 in the black and whitish slate, B" 78, Barker street, Castlemaine ; 

 in the black flags of B^ 29, Newham, section 20 ; B" 27 ; B" 80, 

 gully running from E. into Kangaroo Creek, S. of township ; 



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