Graptolites. 285 



refers it to the group with a double series of cells. The figure 

 is too broad for a species of Graptolithus, and the length and 

 general aspect agree better with Diplograpsus, so that I do 

 not hesitate, with Hall, to refer it to that genus. Moreover, 

 Hisinger's Grajptolithus (Prionotus) scalaris, collected in the 

 same locality as that in which Linnaeus obtained his fossil, is 

 undoubtedly the species that was afterwards described by 

 M'Coy under the name of Diplograpsus rectangularis. 



Grajptolithus Sagittarius, of the twelfth edition of the 

 Sy sterna, has always been quoted as belonging to this tribe of 

 fossils. I cannot imagine how Hisinger came to apply this 

 name to a species of the restricted genus Graptolithus, with 

 which Linnaeus' s description has not one character in common. 

 The original species was founded on the drawing of the frag- 

 ment of a Lepidodendron, a genus of fossil coal plants, in 

 Volkmann's Silesia subterranea (1720), Part III., Tab. 4, Fig. 

 6, which is accurately described in the short diagnosis 

 appended by Linnaeus to his species. This error made by 

 Hisinger has passed through all the works on Graptolites 

 uncorrected, and has caused the Linnean generic name to be 

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

 only species known to Linnaeus was a Diplograpsus. 



We would here object to a practice that has prevailed 

 among some writers on this family of fossils of altering the 

 spelling of generic names to suit their peculiar notions. Unless 

 under very peculiar circumstances, the original spelling should 

 always be retained, and as Linnaeus wrote the generic name, 

 Graptolithus, it ought to be so used. In his Scanian Travels, 

 it appears as Graptolitus, but in the Sy sterna he retains 

 throughout the original spelling. The term Graptolites may 

 be considered to be a useful English form of the word, and may 

 be conveniently employed, as it has been by Barrande, as a 

 common term for the whole family. 



Structure. Believing, with the majority of those who 

 have examined this family, that the graptolites are true 

 Hydrozoa, I shall discard the nomenclature that has crept into 

 use, adopted, as it has been sometimes, from supposed resem- 

 blances to plants, and sometimes from affinities to animals, 

 and employ the terms that have been proposed by Huxley and 

 Allmann, in their works on the recent Hydrozoa. As these 

 terms have not yet got into general use, it will enable the 

 reader better to follow the descriptions if I here give defini- 

 tions of the few that it will be necessary to employ. The 

 observations made within the last twenty years on the Hydrozoa, 

 have shown that every hydroid exists under two separate 

 forms, the one, the " trophosome," destined only for nutrition 

 and growth ; the other, the " gonosome," designed for the 



