146 CANADIAN FOSSILS. 
Some other species besides this have grown as quadrilateraltubes. Those 
specimens which show an undulated margin with projecting mucronate 
points or spinules can be of no other form than that which is here described: 
we have good reason to suppose all those with inequilateral stipes to 
belong to the same‘form; and those with deep indentations on one side and 
without cell-markings, except simple undulations on the other side, are 
only another phase, depending upon the direction and degree of pressure. 
The species under consideration, in its various aspects, illustrates more 
fully than any other which we have seen, the effects of pressure in differ- 
ent directions. The cellules, in form and in manner of opening upon the 
surface, differ from such as Graptolithus pristis, and appear to be inter- 
mediate between those of G. bicornis, = Climacograptus, and those of 
G. ramosus. 
EXPLANATIONS OF FIGURES OF GRAPTOLITHUS QUADRIMUCRONATUS, Hall. 
Puate XIII. 
Fig. 1. Part of a stipe compressed in a slightly oblique direction, still showing the 
cellules'on the two sides. 
Fig. 2. A stipe compressed more obliquely, so as nearly to obscure the cellules on 
one side. 
Fig. 3. A specimen compressed vertically to the celluliferous side of the stipe. ! 
Figs. 4,5, and 6. Enlargements from specimens, figs. 1, 2, and 3 respectively. 
Fig. 7. Enlargement from a specimen where the solid axis lies near to one side. 
Fig. 8. A specimen obliquely compressed, so that the mucronate points at one angle 
of the cellules of the left side, are pressed through the test, and show on 
the surface as a range of pustules. The axis is displaced, and seen on one 
side of the centre. 
Fig, 9. A diagram representing a theoretical longitudinal section. 
Fig. 10. A transverse section of a stipe with the mucronate extensions of the cell- 
margins. 
Formation and Locality—Utica slate formation; Lake St. John, east 
from Blue Point. 
RETEOGRAPTUS EUCHARIS, Hall. (a. s.) 
Plate XIV, fig. 9. 
Frond spreading, nearly flat, consisting of numerous narrow lanceolate 
elliptical stipes, attached to a common initial point-or axis, and bilaterally 
arranged on two sides of a short funicle, which is four or five times bifur- 
cated on each side. 
