GRAPTOLITES. a5 
mon body, not unlike many of the Sertularians, except that the cellules 
are generally close together at their origin.* They are usually more or 
less oblique to the direction of the axis, as is clearly indicated by the cell- 
partitions ; and the degree of obliquity often indicates specific distinction. 
The cellules are for the most part contiguous at their origin, and they 
sometimes remain in contact throughout their entire length ; but in the 
greater number of species there is a small portion of each one free on one 
side towards the aperture. This character is shown in numerous examples. 
(Plates i, 11, and i.) 
In some forms the cellules are contiguous in their lower portions, while 
the entire upper or outer part becomes free, as seen in Gt. Clintonensis 
(plate B, figs. 1, 2, and 3); while in one of the bi-celluliferous species _ 
from Iowa, the cellules are distant from each other at their origin, and the 
upper extremity of one scarcely reaches to the base of the next in advance 
(plate A, fig. 10) ; and they are therefore not properly in contact in any 
part of their length. The same is more emphatically true of Rastrites, 
(fig. 27), where there is a large interval between the bases of the cellules, 
which are often nearly rectangular to the axis. 
Although we regard the cellule as limited by the cell-partitions, yet in 
well-preserved specimens there is sometimes a swelling of the test of the 
common body below the cellule, indicating an enlargement of the parts at 
the bases of the buds. In one species there is an evident undulation of the 
axis, corresponding to this enlargement of the parts in the common body. 
(Figs. 10 and 11, plate A.) 
* The mode of budding and the form and arrangement of the cellules in the Sertula- 
rians are shown in the accompanying figures of two species of Sertularia (figs. 1 and 2) 
from our own coast. Fig. 3, with a range of cellules on one side only, is a Plumularia. 
Fig. 1. Fig. 3.- Fig. 2. 
