GRAPTOLITES. 69 
cation between the series, each of which has its common body or canal, 
as in those with the single series of cellules. This character is clearly 
shown in some of the bi-celluliferous species, which subdivide above the 
base by the dehiscence of the axes. 
The species having a single series of cellules are developed in a bilateral 
arrangement of the parts on the two sides of a central point or radicle. 
The simplest forms known consist of two single elongate stipes ; others 
have four, eight, or more simple stipes ; while in other species the stipes 
are variously bifurcated ; but in all they are symmetrically and bilaterally 
arranged upon the two sides of the specimen. Many of these compound 
forms have the bases of the stipes united in a central corneous dise or cup, 
which is of the same substance as the stipes, thickened in the middle, and 
attenuate at the margins, and which in the living condition was probably 
of a concayo-convex form. 
The centre of these dises on the exterior side often presents a small 
prominence or point, which however does not bear evidence of having 
been attached, at least during the later periods of the animal’s life. 
The species under this genus may for convenience be distributed in 
two sections with several subordinate divisions, as shown on pp. 65 and 66. 
1. GRAPTOLITHUS NITIDUS, Hall. 
Plate I, figures 1-9. 
(G. nitipus, Hall: Geological Survey of Canada, Report for 1857, page 129.) 
Description.—Frond composed of two simple stipes proceeding from 
a small radicle, and diverging at an angle of about 175°. Stipes narrower 
at the base, and gradually widening towards the extremities, which in 
perfect specimens are somewhat rounded from the partial development of 
two or three of the terminal cellules. Radicle short, abruptly tapering to 
a slender point. The stipes in their greatest width are from six to 
ten hundredths of an inch, while near the base they are often not 
more than five hundredths of an inch in, width. The proportion of the 
stipe occupied by the common body is about one sixth, or less than one 
sixth of the entire width. In the broader stipes, the limits marked by the 
pustuliform elevations indicate the bases of the cellules. In some spect- 
mens, one fourth of the width is occupied by the common body. 
Cellules long and narrow, from thirty-two to thirty-four in the space 
of an inch, curving slightly upwards, nearly twice as large at the 
E 
