118 CANADIAN FOSSILS. 
Genus PHYLLOGRAPTUS, Hall. 
Gr. Svarov, folium, and ypadw, scribo. 
(Puytiogrartus: Geological Survey of Canada, Report for 1857, page 135.) 
Generic characters.—Frond consisting of simple or compound foliiform 
stipes, which are celluliferous upon the two opposite sides, the margins 
having a mucronate extension from each cellule: or consisting of ‘similar 
forms united rectangularly to each other by their longitudinal axes, and 
furnished on their outer margins with similar cellules ; the whole supported 
on a slender radicle, or combined in groups. 
These forms are analogous in structure to Diplograptus ; but instead 
of two simple stipes united by their solid axes,'we have in the examples 
illustrated, four stipes united in a similar manner, giving four separate and 
independant sets of cellules. The cellules have hkewise a proportionally 
greater development, giving a broader form to the stipes than in typical 
species of Diplograptus. ‘These bodies, which usually appear upon the 
stone as simple leaf-like expansions, may have been attached in groups to 
some other support ; but the forms of most of them, and the character of 
the projecting radicle ‘at the base, give the same indication of the entire- 
ness of the frond that we have in ordmary forms of Diplograptus. 
Of all the Graptolitide, these forms furnish perhaps the best illustration 
of the lesser development of the cells at the base of the axis, and of their 
eradual expansion above, as far as the middle or upper part of the stipe. 
Many of them diminish from the centre upwards, and rarely the cells are 
more developed above the centre, reversing the usual mode, and leaving 
the narrower part at the base. 
‘When bodies of this form were thrown down upon a muddy sea-bottom, 
they would become imbedded mainly in two positions. The most common 
position appears tobe that in which the parts retain a vertical and a horizon- 
tal direction, as in fig. 1; the lower division or folium d would thus become 
first imbedded ; while the folia 6, ¢ would lie in the plane of deposition, and a 
would be the last imbedded. ‘The slaty lamine separate along the line J, ¢, 
either above or below the folia 6, ¢; leaving on one side the folia and on the 
other their impression. If the separation takes place above, then the bases 
of the cellules of a remain; these are directed obliquely downwards to- 
wards the base of the stipe. If the separation takes place below the folia 
b, c, the cellules of folium d are seen directed upwards, or towards the apex 
of the stipe. ‘These modes of separation ‘would present appearances like 
figs. 4 and 8, pl. xv; fig. 4, pl. xvi; and figs: 5-and 15, pl. xvi. 
The other direction of imbedding would be when the specimens were 
so deposited that the laminze rested obliquely to the plane ‘of stratifica- 
