GRAPTOLITES OF NEW YORK, PART 2 qC 



now of the relation of both the inflations and their central axes to the 

 nemacaulus and virgula. I think it is a priori probable that the vesicles 

 are local inflations of the outer tube (nemacaulus) and that the axes seen to 

 pass through them in D. appendiculatus and the two species of 

 Climacograptus are the central solid rod or virgula proper. An inspection 

 of the appendages of C . parvus leaves indeed no doubt of the truth of 

 this assertion. It is seen that the axis of the vesicles is much narrower and 

 less in substance than the nemacaulus bearing the vesicles. Text figures 

 27 and 31 distinctly illustrate this difference in width. In 27 it is not 

 more than one fourth of the nemacaulus and in 31 about one half. The 

 central axis while containing less carbonaceous substance than the nema- 

 caulus, is still distinctly thicker in most specimens than the walls of the 

 vesicles. All these facts must be viewed as supporting the inferences of 

 the presence of a solid axis within the nemacaulus and the origin of the 

 vesicles from inflations of the nemacaulus. 



In that case it is also more probable that the appendages were real 

 vesicles or inflations than that they formed flat disks or wings of the nema- 

 caulus walls. If they were alate expansions one would, where the vesicle 

 has been split through the middle in the breaking of the shale, thereby 

 exposing the virgula [as in text fig. 35], expect to note the boundary of 

 the canal of the nemacaulus against the solid wincrs but nothing of the kind 

 is observed in the many appendages, and the continuing of the somatic 

 canal into the inflation is everywhere apparent. If the vesicles served as 

 pneumatophores, as has been claimed above, there probably existed a par- 

 tition between the somatic canal proper and the gas receptacles and it is 

 possible that a further separation of the tissues of the wall had taken place 

 which can not be discerned in compressed material. 



In macerated vesicles of Climacograptus parvus the walls are 

 invariably dissolved into strings of fine hairlike fibers, extending longitudi- 

 nally in the direction of the nemacaulus and apparently anastomosing in long 

 intervals, thereby forming very long and narrow meshes [see text fig. 34], whose 

 interspaces are filled by thinner carbonaceous films. This structure would 



