44 CANADIAN FOSSILS. 
The term Diplograptus is properly applied to such forms as Graptoli- 
thus pristis, Hismger, G. palmeus, Barrande (excepting figs. 5 and 6), 
G. foliaceus, Murchison, and G. pristiniformis of this memoir; where the 
cellules are disposed in parallel ranges on the two sides of the central 
axis, and are of the same or similar form and arrangement with those of 
monoprionidian form G. sagzttarius, and with others of that type, in which 
we include all the species of the first nine plates of this memoir ; the reason 
for the proposed separation being in the double range of cellules only. 
In the ordinary forms of Diplograptus (plate xiii, figs. 15-17), as in the 
ordinary monoprionidian types, the cellules are usually closely arranged, 
and overlapping each other for a part of their length. In a single species 
CG. putillus, from the Hudson River formation in Iowa), which has 
come under my observation in some well-preserved fragments, we have 
so far a modification of the general arrangement of the cellules that 
the apex of one barely reaches the base of the next succecding. The 
stipe is a strong elliptical tube with a flattened central solid axis, the 
line of which is marked on the exterior by a longitudinal undulating 
groove (fig. 10, pl. A). The surface is strongly striated transversely, 
and the sides studded with tubular cellules, which are alternately arranged. 
These cellules are sub-oval, flattened on the side adjoming the body 
of the graptolite, curving on the exterior free portion, and obliquely flat- 
tened at the base just above the aperture of the cellule next below, as 
shown in the profile view (fig. 11, plate A). The exterior test of the 
common body is swollen in oblique undulations in the direction of the base 
of the cellules, or where the individual buds take their origin; and the 
axis is curved towards the opposite side, as shown in fig. 10, plate A. 
The transverse diameter of the stipe is about two-thirds as great as the 
longer diameter. The celluliferous face of the stipe shows broad elliptical 
depressions ; the lower side, for little more than half the height, being the sub- 
oval cell-aperture ; while the upper part is the semi-oval flattened area at 
the base of the next succeeding cellule, as shown in fig. 11, plate A. In 
this case the cellules are shown to be separate and distinct tubes, closely 
pressed against the lateral walls of the stipe on one side, and communica- 
ting with the common canal by a slightly narrowed passage, as shown in 
figure 12, plate A, which represents a longitudinal section of the body. 
In a transverse direction the base of the cellule is wider than the aperture 
Cig: dd, spl. A): 
Specimens of this character, on becoming flattened, would present a form 
where the cellules, though inclined against the common body, would not 
overlap each other, and where the margin of the cellule is directed 
backward instead of forward. Were these cellules to be prolonged, they 
would overlap the next in advance, presenting in this condition but a slight 
modification of the usual forms of Diplograptus. These deviations from 
