SUPPLEjSIENT. 499 



however* appear probable that in a family of fossils so closely allied as 

 are all the proper GraptolitidedR, any such great diversity in mode of growth 

 would exist. 



It will appear evident from what follows, that heretofore we have been 

 compelled to content ourselves, for the most part, with describing frag- 

 ments of a fossil body, without knowing the original form or condition 

 of the animal when living. Under such circumstances, it is not surprising 

 that various opinions have been entertained, depending in a great measure 

 upon the state of preservation of the fossils examined. The diminution in 

 the dimensions, or perhaps we should rather say in the development, of 

 the cellules or serrations of the axis towards the base, has given rise to 

 the opinion advanced by Barrandb, that the extension of the axis by 

 growth was in that direction, and that these smaller cells were really in 

 a state of increase and development. In opposition to this argument, we 

 could before have advanced the evidence furnished by G. bicornis, G. 

 ramosus, G. sextans, G. furcatus, G. tenuis, and others, which show that 

 the stipes could not have increased in that direction. It is true that none 

 of the species figured by Barrande indicate insuperable objections to this 

 view ; though in the figures of G. serra ( Brongniart), as given by Geinitz, 

 the improbability of such a mode of growth is clearly shown. 



It is not a little remarkable that with such additions to the number of 

 species as have been made by BarHanbe, M'Coy and Geinitz, so few ra- 

 mose forms have been discovered ; and none, so far as the writer is aware, 

 approaching in the perfection of this character to the American species. 



Maintaining as we do the above view of the subject, which is borne 

 out by well-preserved specimens of several species, we cannot admit the 

 proposed separation of the Graptolites into the genera Monograpsus, Di- 

 plograpsus and Cladograpsus, for the reason that one and the same species, 

 as shown in single individual.?, may be monoprionidean or diprionidean, or 

 both ; and we shall see still farther objections to this division, as we 

 progress, in the utter impossibility of distinguishing these characteristics 

 under certain circumstances. We do not yet perceive sufficient reason to 

 separate the branching forms from those supposed to be not branched ; 



