GRAPTOLITES. vi 
from five to nine hundredths in their different stages of growth and devel- 
opment. .The common body occupies a very small proportion of the 
entire width, and its limits are not distinctly defined. Surface of stipes 
quite smooth ; test very thin, and cell-walls usually obscurely marked. 
Cellules of moderate length, from twenty-four to twenty-six m the 
space of an inch, and inclined to the axis at an angle of about 32°, as 
indicated by the lines of the cell-partitions : line of the aperture truncate, 
or very slightly convex, making an angle of 120° with the axis, and 
nearly rectangular to the direction of the cellule. The cellules, in their 
lower part, and for two thirds of their length, are straight, and scarcely 
wider throughout than at their origin: at this point, just before becoming 
free, they are abruptly expanded on the posterior side, and this margin 
of the free extremity makes a larger angle with the direction of the axis. 
This expansion of the cellule is perhaps as properly a sudden constric- 
tion just below the orifice, or at the base of the cell-denticle. The cell- 
denticles, under a strong lens, are seen to be finely striated parallel to 
the line of the aperture. 
This species in its mode of growth and general form resembles G. patulus, 
but in its development it earlier attains the full width of the stipe. It 
is always smoother on the exterior surface, and the cell-walls rarely make 
distinct strize, as in that species, though this character is visible under a 
lens. The form of the denticles is however very characteristic; and 
this at once distinguishes it not only from G. patulus, but also from every 
other species of this group. It is associated in the same slates with 
G. patulus and G. quadribrachiatus. 
A specimen in the shales of Gros Maule, preserving all the essential 
features of this species, has apparently a thicker test, and the interior is 
partially filled with stony matter, so that the parts are more clearly seen. 
In this one the cells show a very gradual expansion towards the aperture, 
and a slight curvature of the cell-partitions near the base, while the con- 
striction below the cell-mouths is more strongly pronounced. 
EXPLANATIONS oF Figures or GRAPTOLITHUS consTRICTUS, Hall. 
PuateE I. 
23. A young individual of the natural size. 
24, An older specimen. 
25. A part of a much more extended stipe, but which is not wider than fig. 23. 
26. A part of a stipe from Gros Maule. 
27. An enlargement showing the form of cells, the cell-denticles or apertures, and 
the characteristic apparent constriction. ' 
Formation and Localities.—Shales of the Quebec group; from some 
loose masses below the village of Point Lévis, and from Gros Maule. 
