190 TWENTIETH REPORT ON THE STATE CABINET. 



I am able to corroborate, to some extent, the observations of M. Barrande 

 in regard to the apparent double character of this axis. In some extremely 

 compressed specimens, it is marked by a longitudinal groove or line of divi- 

 sion ;* while in others, a double impression has been left by the removal of 

 the substance. 



In. some specimens, particularly the younger ones, the solid axis has 

 been seen extending beyond the base of the stipe, as a duplicate process, 

 exhibiting a character as of a double radicle. In several species there is 

 on each side a lateral process of similar character, extending rectangular- 

 ly or obliquely downward from the base of the lower cellules, and usually 

 having a greater length than the initial point itself. This feature is shown 

 in the germs and young graptolites on Plate i, and in figures of Graptoli- 

 thus {Climacograptus) bicornis, Plate ii. The same feature is shown in a 

 more extreme degree in G. (C) aiitennarius of the Quebec group. t In 

 some solid specimens of one species, where the tube has been filled with 

 calcareous mud, I am able to detect only a single round point in the 

 centre of a transverse section ; and a longitudinal section of the same 

 species presents a slender filiform axis. It may be, however, that the 

 parts are so minute and so closely united, as to render them undistin- 

 guishable. 



In another species, with two rows of cellules, and in which the latter 

 are of very difi"erent form from the preceding, the solid axis is a thin flat 

 apparently double plate, extending across the entire transverse diameter 

 of the tube, which is more than two thirds as great as its longer diameter. 

 The place of the axis is marked by a longitudinal groove on each side, not 

 in a direct line, but slightly undulating to correspond with the cellules 

 (PI. ii, fig.lO). M. Barrande conceives that the joining of the two plates 

 of this axis may leave a very flat intermediate tube ; and in our specimen, 

 there is apparently an extremely narrow space between the two. He 

 farther supposes that each of these plates, composing the double axis, is 

 separable, by decomposition, into two laminae, as illustrated in Plate iii, 

 fig. 3, of the work already cited. 



The entire appearance of the species (Plate ii, fig. 10), is that of two 

 monoprionidian stipes joined together at the back, the line of junction 

 being indicated by the groove. 



In one species of Retiolites, there is a strong excentric or sub-exterior 

 axis, which is nearly direct ; and in the same individual there is another 

 undulating axis, to which the cell-divisions of one side are attached. In 



• Tho aspect presented by the axis, when marked by a longitudinal groove, is precisely 

 that which a hollow cylindrical body would have if extremely compressed. 



t Graptolites of the Quebec group, Decade ii. Geol. Survey of Canada, plate 13, figs. 

 12 and 13. 



