GRAPTOLITES OF NEW YOHK, PAUT 1 



613 



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Fig. 34 Staurograptus dichoto- 

 m u s Emmons. Copy of original figures 



The only note on the genufc,, which is known to me, is that by Hall 

 [1865, p.43] which reads : " The typical and only species of Staurograptus 

 of the same author is a very remarkable forai of extremely minute pro- 

 portions. Its mode of growth and subdivision of stipes, if accurately repre- 

 sented in the figure, are unlike anything known among this family of 

 fossils, and it merits generic distinction." Lapworth refers to it [1887, p.l68j 

 as the "dubious genus Staurograptus of Emmons." 



I have i\o\\- found in the same region whence Emmons obtained this 

 material, in slates associated with the Upper 

 Cambric Dictyonema flabellifonne bed, a com- 

 plete series of growth stages [pi. 2] leading 

 from the sicula through stages identical with ^_ _ ^^-^ 

 Emmons's Staurograptus dichotomus *^ " ^ 



to Clonograptus proximatus, a 

 species described by Matthew from the Upper 

 Cambric of the St John basin. Though the 

 mature specimens of the species look very different from the growth stage 

 which Emmons happened to have, the right of priority requires, I think, 

 the recognition of his generic and specific teims. 



It is evident from Emmons's description that he considered his specimen 

 as full grown, and as having noimally " dichotomous cells tenninal," but this 

 does not vitiate the fact of his recognizing the differential character of this 

 form, consisting in the cruciform center. 



The recognition of the generic term Staurograptus would make Hall's 

 term Clonograptus a void synonym, in case the mature form here described 

 should be referable to the latter genus. It is however certain that the 

 forai presents, in its mature stage, characters of Hopkinson's genus Clemato- 

 graptus [1875, p.652]. The latter is characterized in its type species, 

 CI. i m p 1 i c a t u 8 Ilopk., by the radial disposition of its branches, which 

 branch so closely to the sicula that they all appear to spring at once from 

 the center, and that the "funicle " of other Dichograptidae is hardly notice- 

 able. This concentration of branching of the rhabdosome in the early 



