. Annual report . rrespond-ing to the vertical lines of an H, while the primarybranches form the connecting bar. The sicula islong and the primary thecae diverge from the proxi-mal part of the same. This group has the same structure as Tetra-graptus, viz a twice repeated bifurcation. It is,however, in the character of its thecae, the point ofbranching of the primary thecae and the direction two thecae and of those of the assumed by the branches of the second order totally proximal portions of the branches. J J x6 (Copy trom Holm) different trom the other species of Tetragraptus; and it can be
. Annual report . rrespond-ing to the vertical lines of an H, while the primarybranches form the connecting bar. The sicula islong and the primary thecae diverge from the proxi-mal part of the same. This group has the same structure as Tetra-graptus, viz a twice repeated bifurcation. It is,however, in the character of its thecae, the point ofbranching of the primary thecae and the direction two thecae and of those of the assumed by the branches of the second order totally proximal portions of the branches. J J x6 (Copy trom Holm) different trom the other species of Tetragraptus; and it can be easily proved to belong to an entirely different series from theother four branched forms [, ]. The very slender thecae, the result-ing very thin, tiexuous branches, the peculiarly long sicula and, specially, thedivergence of the primary thecae at a point high up near the apex indi-dicate that T. (Etagraptus) lent us, the type of the subgenusbelongs in one group with Groniograptus perflexilis, is closely. )tj Tetragraptus s i m i 1 i sHall sp. Proximal part seen frombelow. Shows the apertures of thesicula (in the center), of the first 1 In allusion to the similarity of its form to the Greek letter II. GRAPTOLITES OF NEW YORK, PART 1 645 related to Sigmagraptus praecursor and Coenograptus, tliouglinot their progenitor, and, very probably, leading to certain flexuous forms ofDidymograptus. Tetragraptus quadribrachiatus Hall (sp.) Plate 11, figure 1-4 Graptolithus quadribrachiatus Hall. Geol. Sur. Can. Rept for 1857. 1858. crucial is Salter. Quar. Jour. Geol. Soc. 1863. 19:137, %.8bGraptolithus quadribrachiatus Hall. Canadian Organic Remains, decade 2. 1865. , , ; , ,6Tetragrapsus quadribrachiatus Nicholson. Quar. Jour. Geol. Soc. 1868. 24:131Of. Graptolites (Didymograpsus) quadribrachiatus McCoy. Jour. Geol. Sur. Victoria. Prodr. Pal. Victoria, decade 1. 1874. , , Tetragraptus quadribrachiatus Etberidge j
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