72 CANADIAN FOSSILS. 
Cellules distinctly limited by the partition-walls, about from twenty-four 
to twenty-six in the space of an inch ; rather wide, making an angle of about 
60° with the direction of the axis, and slightly curving upwards; their pro- 
portions vary according to the width of the stipe, bemg from three to four 
times as long as wide. Outline of the aperture curved, concave, making an 
angle with the axis of about 130°; on the lower or posterior side produced 
into mucronate points which curve gently forward: walls of the cellules 
distinctly striated parallel to their margins, for one half the depth. The 
anterior margin of each cellule is vertically above the base of the second 
cellule in advance. 
Fragments of this species are numerous upon some slabs of greenish or 
blackish-green slate where other species occur. ‘The remains of single 
stipes are sometimes four or five inches in length, showing in different 
individuals little variation in width after becoming perfectly developed, 
which occurs within an inch of the radicle. Sometimes the stipes are 
compressed vertically, and present the smooth limear base or exterior, 
which is less in width than when compressed laterally. The lateral faces 
of the stipes exhibit some variety of surface, dependent on the degree of 
compression, or in some instances, on the replacement or filling of the inte- 
rior by iron pyrites. In these cases, or when the branch is not flattened, 
the surface is deeply striated or wrinkled obliquely. Sometimes when 
extremely compressed, the surface has an appearance of vesicular struc- 
ture, which is probably due to influences attending the mineralization of 
the fossil, or the fillmg up of the original canal. 
This species is palpably different from the last in the greater extent of 
the stipes, and in their almost perfectly linear character. The form of the 
denticles, and their angle with the axis, as well as their proportional dis- 
tance, are distinctive characters. The G. virgulatus of Beck (Geinitz’s 
Graptolithen, page 387, pl. v, fig. 86) bears some resemblance to this 
species in the figure of natural size; but our species does not correspond 
with the enlarged figures. 
EXPLANATIONS OF FiguRES OF GRAPTOLITHUS PATULUS, Hall. 
Puate I, 
10. A specimen preserving the radicle, and a stipe on one side two and a half 
inches in length. 
11. The distal extremity of a larger stipe. Some of the cells are filled with 
iron pyrites. 
12. A short stipe broken off near the radicle, showing the narrow form near the 
base, and a greater width beyond, exceeding that of the ordinary forms. 
13. A part of fig. 12 enlarged. 
14. A part still further enlarged to show the striz parallel to the cell- -apertures. 
15. An enlargement from fig. 11, where some cells are filled with iron pyrites, 
showing their extension almost to the back of the stipe. 
