THE ANNALS 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 



No. 58. OCTOBER 1872. 



XXXV. — On Callograptus radicans, a new Dendroid Grap- 

 tolite. By John Hopkinson, F.Gt.S., F.R.M.S. 



[Plate X.] 



The genus Callograptus belongs to a group of organisms 

 which are frequently classed with the Graptolites, but which 

 present sufficient points of difference to warrant their sepa- 

 ration as a distinct sub-order, for which the name Den- 

 DROIDEA has been proposed by Prof. H. A. Nicholson. In it 

 are included the genera Ptilograptus^ Bendrograptus^ Gallo- 

 graptus^ and Dictgonema. These forms, while nearly allied 

 to each other, differ considerably from the true graptolites. 

 The slender chitinous rod or " virgula," from the invariable 

 presence of which in the true graptolites Prof. Allman has 

 recently proposed for them the name Rhabdophora, is not 

 present in these forms ; and the slender " radicle," forming in 

 the true graptolites the proximal termination of the virgula, is 

 also absent. The Dendroidea, all of which are branching 

 forms, differ also from the Rhabdophora in their mode of 

 branching, and there seems to be a slight difference in their 

 hydrothecEe. 



There is yet another and a very important point of differ- 

 ence between the two groups. The new species of Callo- 

 graptus^ which I propose to name C. radicans^ seems to fur- 

 nish conclusive evidence of the fixedness of the forms to 

 which it belongs, while the slender tapering radicular jorocess 

 of the Rhabdophora shows that they could not have been 

 similarly attached to foreign bodies. 



Callograptus agrees with its near allies, Dendrograptus 

 Ann. (fc Mag. N. Hist. Ser. 4. Vol. x. 18 



