23 CANADIAN FOSSILS. 
frequently seen extending beyond the celluliferous portion of the stipe at 
_its outer extremity ; while the radicle appears like the continuation of the 
same below the base. ‘The axis thus appears to be the foundation on which 
the other parts are erected. In those specimens, however, which present 
so great an extension of the solid axis beyond the stipe, the cellules may 
have been removed by subsequent causes. 
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 ex- 
tremely compressed specimens it is marked by a longitudinal groove or 
line of division ;* 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 some solid specimens of 
one species, where the tube had been filled with calcareous mud, I am 
able to detect only a single round point; 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 undis- 
tinguishable. 
In another species, with two rows of cellules, and in which the latter 
are of very different 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. 
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 appa- 
rently 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 lamine, as illustrated in plate ii, fig. 3, of the 
work already cited. 
The entire appearance of the species (plate A, 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 fetiolites 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 
the Retiolites of the Quebec group, one side of the stipe shows a very 
distinct axis, while upon the other side it is very obscure. 
In Retiograptus we have a very distinct central axis projecting below 
* The aspect presented by the axis, when marked by a longitudinal groove, is pre- 
cisely that which a hollow cylindrical body would have if extremely compressed. 
