TEANSACTIONS OF THE SECTIONS. 71 



On the Nature and Systematic Position of the Graptoliticlce. 

 By Henky Axletne Nicholson, D.Sc, M.B., F.G.S., ^c. 



The author of this paper, after stating the views of those who had referred the 

 Graptolitid£e to the Cephalopoda, the Actinozoa, the Polyzoa, and the Foramimfera, 

 stated the reasons which induced him to chiss them with the Hydrozoa, a view 

 originally put forth by Prof. M<Coy. This opinion was shown to be supported by 

 the moi-phology of the Graptolitidae, and especially by the existence of a " common 

 canal" corresponding to the "ccenosarc" of the Hydi-ozoa, from which arose the 

 separate cellules or polypites. As a special morphological point, it was also mdi- 

 cated that the " central disk " of some Tetragrapsi and Dichograpsi would find 

 a feasible homologue in the "float" or " pneimiatophore " of the Physophondfe, 

 an order of the oceanic Hydrozoa. 



Passing from the nutiitive to the generative system, the author drew attention 

 to the bodies originally described by himself as the "ovarian vesicles" of Grapto- 

 lites, and also to those previously described by Hall, pointing out their close affinity 

 with the " gonophores " of the recent Hydrozoa. 



The reference of the Graptolitida; to the Hydrozoa was further shown to be 

 supported by their mode of existence and by the determination of allied forms. 

 As regards the former point, proofs were adduced that the great majority, if not 

 the whole, of the Graptolitidffi were free and unattached, an almost fatal objection 

 to the belief that they were referable to the Bryozoa. As to the second point, 

 attention was drawn to the existence of a form (origiually described by the author 

 under the name of Corynoides calicidaris) which was closely allied^ to the Grap- 

 tolites, but which probably represented the Corynidaj or Tubularidte in the Silurian 



seas. 



The author, in conclusion, declared his belief that the Graptohtidaj could not be 

 referred to any existing order, or even subclass, of the Hydrozoa, standing there- 

 fore in the same relation to the latter that the Trilobites do to existing Crustacea. 

 In the present state of om- knowledge it seemed, therefore, most advisa-ble to con- 

 sider the Graptolites as constituting a new subclass intermediate iu position 

 between the oceanic and the fixed Hydrozoa ; and there were some reasons for 

 the belief that they perhaps represented the original stock, from which the above 

 existing sections of our living Hydi-ozoa have primarily diverged. 



On the Graptolites of the SJdddmu Slates. 

 By Henry Alieyne Nicholson, D.Sc, M.B., P.G.S., Sfc. 



The author of this communication gave a brief description of the Graptolitesof 

 the Skiddaw Slates, a group of rocks forming the base of the gTeat Silurian series 

 of Cumberland and Westmorland. These Graptolites had been described in 186-3 

 by Mr. Salter, who gave a list of thirteen species. Eejectiug some of these, the 

 author was now enabled, by the researches of Prof. Harbiess and himself, to de- 

 scribe twenty-three species, of which muuber thirteen are well known in the 

 Quebec "-roup of Canada, three are new, and the remainder occur elsewhere, eitlier 

 in the Lower or Upper Llandeilo rocks. The author pointed out various peculi- 

 arities in the forms and distribution of the Skiddaw Graptolites, and showed that 

 by their aid we were able clearly to correlate the Skiddaw Slates vsdth the Quebec 

 fiTOup in Canada. 



The Graptolites of the Skiddaw Slates were shown to be referable to six genera 

 certainly, perhaps to eight. The genus Dichof/rapsus, Salter, was repres^ented by 

 four species, viz. D. Loffani, Hall, D. octobrachiatus, Hall, D. onultiplex, Nich., and 

 D. reticulatus, Nich. Of the genus Tciraf/rapsus, Salter, four species had also bueu 

 identified, viz. T. hryonoides, Hall, T. quadnbrachiatus, Hall, T. Headi, HaU, and 



T. cnicifer, Hall. , , n i • p 



The o-enus Beiidroyraimis, Hall, was doubtfully represented by branching trag- 



ments apparently referable to I). HcdUamis, Prout, from which i>. furcattda of 



Salter appears undistinguishable. 



The genus Pkurograpsus, Nicholson, was also doubtfully represented by a single 



new species, provisionally named P. vagans. 

 Of the genus Diployrapsus, M'Coy, foiu' species are known from the slates, viz. 



