GRAPTOLITES. YH 
the base of the cellule is seen to be much wider than the orifice. (Plate 
A, fig. 10.) : 
In many of the species a transverse section of the cellule near the base is 
quadrangular, becoming more rounded towards the aperture; and when the 
upper part of the cellule is free, the aperture is round or elliptical, and in 
some specimens the calycle is elliptical or cylindrical throughout its 
entire length: We have examples of the quadrangular cellules in G. 
extensus (plate ii, fig. 16) and G. octobrachiatus (plate vii, figs. 5 and 
7); as well as in two species of Phyllograptus (plates xv and xv). 
Where the cellules are more nearly isolated, they approach more and 
more to the cylindrical form. As examples of cellules contracted towards 
the aperture, we have Graptolithus priodon, Barrande, and G. Clinton- 
ensis, Hall. (Plate B, figs. 1, 2, and 3.) 
M. Barrande has remarked that from the circumstance of the partial 
or complete isolation of the successive alveoles of the same series, we may 
easily conceive that the walls of contact in contiguous cellules should be 
double. This fact he has ascertained from decomposing specimens of G. 
priodon ; and we have the same evidence in some of our species. In the 
cellules of the ordinary mode of development, each one is an independant part 
of the organization, and is provided with its individual body and c¢ell-walls, 
as if each cellule were isolated. Whenever two of these are in contact, 
the cell-walls coalesce as far as the contact continues ; but when becoming 
free, the cellule assumes its normal condition. In some specimens of 
Phyllograptus we find this evidence of double walls in the cell-partitions. 
In G. putillus, illustrated on plate A, figs. 10, 11, and 12, the cell- 
walls, although contiguous to and adjoming the walls of the body (and 
not free), do not coalesce, but are readily separable without fracturing 
their substance. 
There are cellules however where the production of the calycle by 
budding from the common body is not so obvious. These forms are 
like G. bicornis and G. antennarius, where the orifice is a simple trans- 
versely-oval aperture in the side of the stipe. In the flattened speci- 
men it appears like a rectangular or slightly oblique, semi-oval notch in 
the margin. Its true form is perceived only when the cavities of the polyp 
have been filled with mineral matter, or when the stipes are flattened ver- 
tically agamst the apertures: they then give the form which has been 
described as G. scalaris. This form of cellules is shown on plate A, figs. 
1 and 2, which are enlarged from a specimen retaining nearly its original 
proportions. Just within the limits of the cellules, and extending the entire 
length of the stipe, there is a longitudinal depressed line; and along this 
line, and running thence almost rectangularly to the outer limits of the 
stipe just above the aperture, the cell-partitions join the exterior test, and 
project in an extended border or flange. 
