76 CANADIAN FOSSILS. 
inch. The apex of the cell-denticle or aperture is a little forward of the 
tubercle marking the base of the second cell in advance. ‘The cell- 
partitions or septa are not strongly marked, but distinct under a lens, and 
terminate below in a minute rounded process or pustule. 
(The specimen on which this description is founded is a fragment 
of two and a half inches long. Other fragments on the same piece of 
weathered shale appear to be identical with it, but are too obscure for 
satisfactory determination. It is supposed to be a bibrachiate form.) 
This species bears considerable resemblance to the figure of G. tenuis 
of Portlock, as given by McCoy (Brit. Paleozoic Fossils, pl.i. B, fig. 4 a, 
b); but the stipe of that one shows no pustule at the base of the cell-division. 
The original figures of Portlock do not however correspond so nearly with 
our species in its cellules, while the axis is not so strongly developed. 
Compared with any of the Canadian forms, except G. extensus, it is 
proportionally narrower ; with that one it corresponds in the number of 
serratures in the same space ; but the angle made by the cellules with 
the axis is very different, and the presence of pustules is a distinguishing 
feature. From all other analogous forms, this one varies in the form, 
proportional number, and inclination of the cellules. 
EXPLANATIONS OF Figures oF GRAPTOLITHUS EXTENUATUS, Hall. 
Prats I, 
21. A fragment of the stipe, natural size. 
22. A portion of the lower extremity enlarged ; a part of the specimen retaining 
the substance of the fossil, and a part being an impression in the slate. 
Formation and Locality.—Shales of the Quebec group; Point Lévis. 
6. GRAPTOLITHUS consTRIcTUS, Hall. (n. s.) 
Plate I, figures 23-27. 
Description—Frond composed of two slender stipes, which diverge 
almost rectangularly from a minute radicle, or are usually bent a little back- 
wards, a feature which is more conspicuous in young individuals. The 
stipes attain their full dimensions near the radicle, maintaining nearly an 
equal width throughout their length : the extremities are somewhat rounded 
from the partial development of some of the terminal cellules. The stipes 
in their greatest width are about nine hundredths of an inch, and vary 
