GRAPTOLITES. 79 
EXPLANATIONS oF Figures OF GRAPTOLITHUS sIMILIs, Hall. 
Puate II. 
1. A very young individual of this species. 
2. An individual somewhat more matured. 
3, An enlargement showing the form of the radicle, and the cells near their origin, 
with a non-celluliferous space between. 
4. A fragment of a longer stipe, which is imperfect at both extremities. 
5. An enlargement of fig. 4. 
Formation and Locality —Shales of the Quebec group; three miles 
above the river St. Anne. 
8, GRAPTOLITHUS ARCUATUS, Hall. (n. s.) 
Plate II, figures 6-10. 
Description —Frond consisting of two simple widely divergent stipes 
proceeding from a small radicle, and bent backwards or downwards, mak- 
ing on the upper side nearly or more than a right angle with the direction 
of this radicle, and then curved gently upwards; presenting a broadly 
arcuate stipe gradually expanding in width from the base to the extremity, 
and celluliferous throughout its entire length. A single denticle, or 
similar process, appears above the rootlet. Radicle short, obtusely 
pointed. The stipe is from four to ten hundredths of an inch in width. 
The cellules reach nearly to the back of the stipe, leaving a narrow space 
to be occupied by the common body. ‘Test extremely compressed in the 
specimens examined, and towards the extremity of the cellules almost 
transparent. The whole has a white or silvery lustre (probably due to 
iron pyrites), and no lines or striz are visible except those marking the 
separation of the cellules. 
Cellules narrow and very little expanded towards the aperture, about 
twenty in the space of an inch, slightly curving upwards, and inclined to 
the axis at an angle of about 30°, varying a little with the curvature and 
development of the stipe ; from three and a half to four times as long as 
broad. Cell-apertures slightly curved, nearly vertical towards the poste- 
rior side and arching towards the anterior side. The apex of the denticle, 
or posterior side of the aperture, is vertically above the base of the third 
cellule in advance of it. 
In some specimens the radicle is broken off, and there is a process on 
the opposite side, giving the appearance of a radicle on the celluliferous 
