X BRITISH GRAPTOLITES. 



especially as lie considers that the specific names of G-raptolites have been too much 

 multiplied, varieties resulting from the efFects of " alteration and deformity " being 

 described as different species. 



j^g42 Eichwald, in 1842 (' Die Urwelt Russlands '), described 



Eichwald, and figured under the new name of Gorgonia flabelliformis the 



' Die TJrwelt Euss- same form as had been previously described as a moss by von 

 lands.' Bromell, and as a monocotyledonous plant by Hisinger. Eich- 



wald l^elieved, however, that it was the impression of a coral resembling Fenestella. 

 ,g^2 III ^li6 same year Vanuxem noticed the occurrence of Gr. 



Vanuxem, dentatus and Gr. scalaris in the Utica slates of America, and 



'Geological Report of figured an example of the former species. He distinctly 

 the 3rcl District of advocates the vegetable nature of the Graptolites : " The 

 ^^ *^' ^' ramose nature of two of the species shows that their origin is 



vegetable, not animal as conjectured by some naturalists. Their chemical com- 

 position confirms their vegetable nature ; no animal ever existed whose material 

 was almost entirely carbon, as is the case with these fossils." 



■ig,g The appearance of Portlock's ' Report on the Geology of 



PortlocJc, Londonderry and of Parts of Tyrone,' which was published 



' Eeport on tlie Geology in 1843, marks a distinct epoch in the history of our knowledge 



of Londonderry and gf ^\^q Graptolites. His work, however, was rather pro- 



Far s o yrone. plietic than conclusive, for his own personal researches on the 



various species of Graptolites, even when reinforced by the work done by previous 



observers, were wanting in that knowledge of the details of structure which 



Barrande subsequently obtained. But Portlock's acumen was so great that he 



deserves a place second only to Barrande, and he may be regarded as the precursor 



of the new era which Barrande subsequently founded. 



Portlock describes and figures nine species of Graptolites : six of these had been 

 named by previous authors, namely, GraptoUtJius coiivolutus, Gr.foliaceus, Gr. folium, 

 Gr. iiristis, Gr. Sagittarius, Gr. scalaris ? whilst three — Gr. Sedgwickii, Gr. distans, 

 and Gr. tenuis — were new forms named by himself. 



Portlock strongly advocated and endeavoured to demonstrate the polyp-like 

 character of the Graptolites, and he controverted the view that they were allied 

 to the Orthoceratites. The presence of septa may, he considers, merely indicate 

 the connection of the polyp cells with an internal axis. The double and single 

 Graptolites, according to him, seem more analogous to Sertularia and Plumularia, 

 but differ in having neither branches nor pinnse. The cell-like structure seen 

 in a scalariform view is analogous to that seen in the Cellaria. Portlock 

 considers that it is probable that there are several Graptolite genera belonging to 

 even more than one order. He does not, however, suggest new names for these 

 genera, and the species described are all grouped by him under the single old 

 generic name Grajitolithus of Linmeus. 



