88 CANADIAN FOSSILS. 
third division is seen lying nearly vertically in relation to these. The 
fourth division has been broken off in the separated film of slate. 
25. A specimen showing the lateral faces of two divisions. Below these, in the 
shale, are seen the non-celluliferous edges of the two other divisions. 
29 and 30 show a still closer arrangement of the parts, and the contiguity of 
the non-celluliferous edges at the apices, which are scarcely perceptibly 
separated in the shale. 
26. An individual where the apices of the divisions are in contact, either conjoined, 
or accidentally so placed, with a narrow space in the centre. In obscure 
specimens it is difficult to separate such forms from Phyllograptus. 
27. An individual where the divisions are equally spreading: one of them presery- 
ing only the base of the stipe. 
28. The same enlarged. 
Formation and Locality.—Shales of the Quebec group; Point Lévis. 
13. GRAPTOLITHUS DENTICULATUS, Hall. 
Plate IV, figures 12-16. 
(G. DENTICULATUS : Geological Survey of Canada, Report for 1857, page 132.) 
Description.—Frond consisting of four simple stipes proceeding from a 
simple radicle. Stipes slightly ascending at their origin, but immediately 
and strongly recurved, again bending gently upwards from the middle to- 
wards the extremities ; slender at the origin, and gradually expanding to a 
width of from nine to twelve hundredths of an inch (exclusive of the den- 
ticles), which it almost uniformly maintains. Substance of the stipe ex- 
tremely thin, and marked on each margin by a linear filiform ridge, like the 
ordinary solid axes of these bodies. In the impressions left on the removal 
of the substance, each margin shows a continuous filiform groove in the 
place of the thickened or solid margin of the stipe; the groove on the 
celluliferous or denticulate side being much stronger than that on the back 
of the stipe. Surface apparently smooth throughout. Cellules consisting 
of small mucronate equilateral denticles, placed vertically on the margin 
of the stipe, and rising immediately from the thickened solid edge: den- 
ticles spreading below, slightly curving, and united at their bases by a thin 
pellicle ; varying in their distance on different parts of the stipe, and 
apparently in different stages of growth ; sometimes twenty-four in the space 
of an inch, near their origin, while elsewhere the average number is from 
eighteen to twenty ; the lower numbermarking the strongest stipes measured. 
This species is very peculiar, differing not only from the associated 
species, but from all others in the arrangement of its denticles. 
