g6 NEW YORK STATE MUSEUM 



exactly correspond to the meshwork of growth lines observed by Wiman in 

 the apical or embryonic part of the sicula of a Diplograptus [see Mem. j,, 

 text fig. 2]. Since the nemacaulus is a direct proximal continuation of this 

 part of the sicula, it is to be expected that it is identical in wall structure 

 with the latter and the observation of such structure in the walls of the 

 vesicles can be considered as a further argument for the view that the 

 vesicles are inflations of the wall of the nemacaulus. 



The "several obscure, obliquely directed fibers running from it (the 

 virgula) on either side outwards and proximalwards " observed by Gurley 

 [1896, p. 7 7, see text fig. 20] in C. parvus are fragments of the same 

 structure, but there is no organic connection between the virgula and the 

 fibers and the aspect similar to the venation of a leaf is merely accidental in 

 Gurley's type. 



e Note on the extension of the virgula into the nemacaulus in the Axonophora 



The writer has in part 1 [p. 487] proposed to distinguish sharply 

 between the hollow, tubular process extending from the 

 proximal end of the sicula to the primary disk in both the 

 Axonolipa and Axonophora, and the solid rod forming in 

 the wall of the sicula in the Axonophora ; by applying 

 to the former the terms nema (in the Axonolipa) and nema- 

 caulus (in the Axonophora) and restricting the use of the 

 term virgula (applied by some authors to the tube) to the 

 solid rod. Of the latter, the writer had already in 1895 



claimed that it extends into the nemacaulus and thus COn- 

 rig- 37 (jlossograp- 

 tusquadrimucro-. . . iii TM • " -1 



n a t u s (Haii). Young tinues into the rhabdosome. 1 Ins assertion was mainlv 



rh.ibdosome showing ne- 



co a py l fr U om Rutdemann^' based on the observation of a specimen [see text fig. 57] 

 of Glossograptus quadrimucronatus in which obviously the 

 solid virgula had been forced out of the nemacaulus by a bending ot the 

 latter This view has lately been verified by two groups of observations. 

 First, A. Schepotieff [1905, p.79 ff] has been able to demonstrate by thin 

 sections the presence of a solid rod in the nemacaulus of species o\ Mono- 



