their Structure and Affinities. 71 



minute ciliated free- swimming organisms, which subsequently, and 

 as a later development, acquired a corneous envelope." I would be 

 glad to have some light on this novel mode of reproduction. I con- 

 fess my inability to understand it. My impression is — but I express 

 it with diffidence — that Dr. Nicholson has somehow confounded the 

 external bell -shaped gonothecae of the Sertulariadce and the gono- 

 phores they contain, and that some clauses in the sentences quoted 

 refer to the gonothec£e and some to the gonophores. 



The generic name Graptolithus was first employed by Linnaeus in 

 the original folio edition of his famous " Systema Naturae" (1736), 

 for certain natural objects which he describes as resembling, but not 

 being, true petrifactions. Not a single form of the fossils to which 

 the name is now confined had a place in the genus till the twelfth 

 edition of the '^ Systema," in 1767, and of the eight species recorded 

 there only one is a true graptolite. This he named G. scalaris, and 

 quoted for it the illustration and description in his Scanian Travels 

 (1751), p. 147, There can be no doubt that Hall is right in re- 

 ferring this species to that which is generally known as Biplograpsus 

 rectangular is, M'Coy. The " Systema" is always, though erroneously, 

 quoted for another species, G. Sagittarius. Linn^us founded this 

 species on the drawing of a fragment oid, Lepidodendron in Yolkmann's 

 "Silesia subterranea" (1720), part iii., tab. 4, fig. 6, and accurately 

 described it in his short diagnosis. Hisinger, in some unaccountable 

 way, applied the name to a species of the restricted genus Grapto- 

 lithus with which Linnaeus' s description has not one character in 

 common. This error has passed through all the works on grapto- 

 lites uncorrected, and has caused the Linnaean generic name to be 

 applied to the species with one series of cells, whereas the only 

 species described by Linn^us had a double series of cells. 



The difficulty of confining the original name to one of the various 

 items included in the genus, and especially of applying a word to 

 these organic remains, which its author employed to indicate that 

 the species included under it were imitations of and not real fossils, 

 presented itself to those who after Linnaeus studied this group. 

 Nilsson proposed Priodon, but as Cuvier had used it for a genus of 

 fish, he altered it into Prionotus. This was first published by 

 Hisinger in 1837. Before this (1835), however, Bronn had pub- 

 lished the name Lomatoceras, but this name had also been previously 

 employed. The original name was restored by Murchison in his 

 "Silurian System" (1839), in a slightly altered form {Graptolites) 

 which has been adopted by British authors. A note by Beck on the 

 family was printed in the same work, and he retains the original 

 spelling, in which he is followed by writers abroad. Under this 

 name all the forms described by Hisinger, Murchison, Portlock, 

 Hall, Geinitz, and others, were included. 



Barrande first subdivided the genus (1850), by separating two 

 marked forms under the names Rastrites and Retiolites, and by 

 forming two sections of the limited genus Graptolithus, — Monoprion 

 for those with a single series of cells, and Biprion for those with a 

 double series. M'Coy in the same year gave these sections a 



