140 Hall on the 



subject are, Les Graptolites de BohSme, par J, Barrande, 1850; 

 Synopsis of the Classification of British Hocks, and Descriptions 

 of British Palaeozoic Fossils, by Rev. A. Sedgwick and Frederick 

 McCoy, 1851; Grauwacken Formation in Sachsen, etc., H. B. 

 Geinitz, 1852. 



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

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

 that the animal in its living state was fixed ; while Mr. J. Bar- 

 rande, 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 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 

 entertained, depending in a great measure upon the state of 

 preservation of the fossils examined. The diminution in the di- 

 mensions, 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 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 opposi- 

 tion 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 in- 

 creased 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 (Brong.), 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, McCoy, 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 can- 

 not admit the proposed separation of the Graptolites into the ge- 

 nera Monograpsus, Dip>lograpsus, and Cladograpsus, for the 

 reason that one and the same species, as shown in single indiv 



