48 THE CANADIAN NATURALIST. [Feb. 



In some forms the cellules are contiguous in their lower portions, 

 while the entire upper or outer part becomes free, as seen in G. 

 Clintonensis, while in one of the bi-celluliferous species from Iowa, 

 the cellules are distant from each other at the origin, and the upper 

 extremity of one scarcely reaches to the base of the next in advance, 

 and they are therefore not properly in contact in any part of their 

 length. The same is more emphatically true of Rastrites, 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. 



In the diprionidian species, the cellules on the two sides of the 

 stipe are alternating, so that the bases or the apertures are opposite 

 the space between two others. 



In much the larger proportion of species, the body of the grapto- 

 lite and the cellules are so extremely compressed, that they appear 

 only as serratures along the margin, with distinct impressed lines 

 marking the cell-divisions. The exterior margin of these serra- 

 tures indicates in an approximate degree the outline of the aper- 

 ture • and the frequently-occurring mucronate extension at the 

 extremity of the cellule is produced by the continuation of the 

 cell-partition, or sometimes by an outgrowth from the margin of 

 the stipe above or below the aperture. 



Were the cellules isolated, their prevailing form would be that 

 of an elliptical tube or sac, the length of which is greater than 

 either of the two diameters. When they are in juxtaposition, 

 however, the contiguous sides are flattened, while the lateral or 

 external surfaces are usually more or less curved, particularly near 

 the aperture. In a larger proportion of the species, the calycle 

 becomes slightly expanded towards the aperture ; but in a few 

 examples there is a distinct contraction above the middle, and >he 

 aperture is smaller than the base. Generally, however, the 

 smaller diameter is just at the junction with the common body, 

 or at the junction of the cell-walls with the walls of the common 



canal. 



In a single diprionidian species, where the specimens are not 



