48 [Assembly 



The radix-like appendages, known in some of our American as 

 well as in some European species, have been regarded as evidence 

 that the animal in its living state was fixed; while M. J. Barrande, 

 admitting the force of these facts, asserts his belief that other species 

 were free. It does not, however, appear probable that in a family of 

 fossils so closely allied as are all the proper Graptolitidece, 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 de- 

 scribing fragments of a fossil body, without knowing the original 

 form or condition of the animal when living. Under such circum- 

 stances, it is not surprising that various opinions have been enter- 

 tained, depending in a great measure upon the state of preservation 

 of the fossils examined. The diminution in the dimensions, or per- 

 haps 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 Barrande, 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. hi- 

 cornis^ G. ramosus, G. sextans, G.ficrcatus, G. tenuis, and others, 

 which show that the stipes could not have increased in that direc- 

 tion. It is true that none of the species figured by Barrande indi- 

 cate 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 Barrande, M'Coy and 

 Geinitz, so few ramose 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 

 Mojiograpsus, Diplograpsus and Cladograpsus, for the reason that one 

 and the same species, as shown in single individuals, may be mono- 

 prionidean 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; for it is not always 

 possible to decide which have or have not been ramose, among the 



