GRAPTOLITES. 109 
Cellules short and comparatively broad, inclined at an angle of about 
25°, free for more than one half their length; the length of cellules about 
two and a half times that of the aperture : margin of the aperture making 
an angle of about 140° with the axis: denticles or cell-extremities short 
and obtuse ; about twenty-eight in the space of an inch. 
This species, in its mode of branching, form, and proportion of cell- 
denticles, differs from any other examined. It has a slight resemblance to 
G. flexilis. 
EXPLANATIONS OF Figures OF DENDROGRAPTUS RAMULUS, Hall. 
Puiate XII. 
9. <A small bifurcating branch. 
10. An enlargement of fig. 9, showing the form and extent of the cellules. 
Formation and Locality.—Quebec Group ; Pomt Lévis, below the 
village, in a loose mass of shale. 
Genus DIPLOGRAPTUS, McCoy. 
Diprion, Barrande ; Petalolithus, Suess. 
Characters—Frond simple (or compound ?). Stipes simple, flattened 
or quadrangular; sides parallel or sub-parallel. Cellules arranged in a 
single series on the two sides of a double central axis: cellules oblique 
to the axis, the cell-apertures opening towards the apex; cell-denticles 
prominent, often mucronate. 
These forms are known only as simple stipes, which are supposed to 
have grown from a fixed root. From analogy with those which I have 
designated Ketiograptus, I conceive they may have grown also in a com- 
pound form, proceeding from a central axis. 
The genera Retiolites, Retiograptus, and Phyllograptus are, in some 
of these characters, similar to Diplograptus ; and some of the latter 
have been included under this designation. The mode of imcrease and 
arrangement of the cellules in those genera presents important differences ; 
and I would propose to restrict the term Diplograptus to such forms as 
are included ia the above description, or those where the arrangement and 
growth of cellules are similar to those of G. pristis, G. palmeus, and 
G. pristiniformas. 
The paucity of species and of individuals of this type is a remarkable 
feature in the collections from the Quebec group. It has scarcely been 
- possible to find specimens for a proper illustration of the spec es. 
