GRAPTOLITES. 73 
Formation and Locality.—Shales of the Quebec group; from loose 
masses below the village of Point Lévis. 
8. GRAPTOLITHUS BIFIDUS, Hall. (un. s.) 
Plate I, figures 16-18 ; Plate III, figures 9, 10. 
Description.—Frond two-stiped: stipes diverging from the small short 
radicle, and curving slightly imward, and thence extending in right lines 
including an angle of from 15° to 20°, varied by growth or accident. Stipes 
very narrow, rounded at the base, and gradually expanding above, attain- 
ing their greatest width at about two thirds of the distance from the base, 
from which they are gradually narrowed to the extremity; they curve on 
the celluliferous margin, and are essentially straight on the back. The 
cellules continuing to increase in length as the stipe is extended to 
the pomt of greatest width, give the peculiar curving outline to the 
celluliferous margin. In the stipes of ordinary width, about one sixth 
of the space is occupied by the common body ; though this proportion 
varies with the development of the stipe. Test thin, nearly smooth, 
or with faint striz parallel to the cell-margins: divisions between 
the cellules strongly marked, and frequently termimating below in 
a minute pustule. The width of stipe varies from one fifteenth of an 
inch at the base, to one eighth or even one fourth of an inch in the widest 
portions. Cellules long and slender, except afew at the base, and some 
partially developed near the apex: the length of the cellules is from three 
to four and a half times their width, according to the degree of develop- 
ment, and they incline to the axis at an angle of 48° near the lower part, 
curving more directly upwards in the middle, or more fully developed part 
of the stipe. Near the base of the stipe the angle of the cellules is greater, 
and towards the apex it is less, until the last few are inclined at a very low 
angle. The cellules are free for from one fourth to one third of their length. 
The apex is extended in a sub-mucronate point. The curving of the cell- 
margin forms an angle of about 120° with the axis in the widest part of well- 
developed stipes. 
This species is very peculiar, differing from all others described in this 
memoir (except G. pennatulus) in the great inequality of width in the 
stipe, and the apparently continuous increase of width from the extension 
of the cellules; while the younger cellules near the apex seem to be 
slowly developed. The stipe at the base is nearly round. Of the earlier 
cellules usually four or five and sometimes six or seven do not attain 
