156 J. HOPKINSON ON BRITISH GRAPTOLITES. 



tolite, which he names G. scalaris. The figure represents a grap- 

 tolite with incised hydrothecae, their apertures being on its upper 

 surface, and from this such specimens have been called " scalari- 

 form impressions." This species does not appear in the " Systema 

 Naturae" until the twelfth edition (1767), the last edited by 

 Linnaeus himself It was the only true graptolite known to him, 

 and he did not consider it a real fossil, but only a mineral aggrega- 

 tion, or " lusus naturae." 



In 1821, Wahlenberg considered that the graptolites of Sweden 

 were orthoceratites. 



In 1828, Brongniart, in his " Histoire des Vegetaux Fossiles," 

 referred them to the Algee, describing two species as Fucoides 

 dentatus and F. serra. 



Nilsson, soon after, referred to them as ceratophydian polypes, 

 and proposed for the true graptolites the name Pi'iodon, a name 

 previously given by Cuvier to a genus of fish. 



Bronn, in 1835, fell into the same error as Nilsson, by substitu- 

 ting the name Lomatoceras, previously given to a genus of insects. 



Hisinger, in 1837, described five species from Sweden, mider the 

 generic name Prionotus. 



Murchison, in the first edition of his " Silurian System " (1839), 

 altered the original name Graptolithus to Graptolites, describing 

 three species ; and Beck added in a note, that he considered grap- 

 tolites nearly allied to Pennatula or Virgularia. 



Geinitz, in 1842, described five species, considering them Cepha- 

 lopoda. 



Portlock, in the following year, first suggested their true affini- 

 ties. In his " Geological Eeport on Londonderry," he recognised 

 them as true zoophytes, allied to Sertularia and Plumularia, and 

 suggested that they should be formed " into several genera, belong- 

 ing even to more than one order." 



Barrande, in a memoir on the graptolites of Bohemia (1850), 

 first subdivided the genus. He established the genera — Rastrites 

 for species having the hydrothec^ separated by a considerable 

 interval; and i?ef2o/2^es, for species which are not true graptolites, 

 having no solid axis, and a polypary of entirely different structure. 

 He also divided the remaining species of the genus GrajJtolithus 

 into two sections — Monoprion and Diprion ; the former having a 

 single scries of hydrothecte ; the latter, a double series. The 

 name Diprion had previously been applied to a genus of insects. 



