GRAPTOLITES. 145 
gently mereasing in width from the base, with the sides parallel 
above. ‘The base is narrow and somewhat obtusely pointed below. In 
what appear to be mature stipes the greatest length is two and a half 
inches ; the width, when flattened and showing two of the four sides, is a 
little more than one eighth of an inch, exclusive of the cell-denticles. 
Test corneous, comparatively thick, and without visible strie. A slender 
axis marks the centre of the stipe, and rarely extends beyond the apex. 
The cellules consist of simple notches or transverse slits in the opposite 
sides, which are slightly dented in the non-celluliferous face, and each 
angle or sinus produced into a slender, mucronate spine, making a range 
of spines upon each angle, or four ranges of spines marking the entire 
length of the stipe; about twenty-two cellules in the space of an inch, 
the margin or lip slightly projecting. 
The specimens of this species occur in great numbers upon the weathered 
and fresh surfaces of some specimens of the Utica slate. Some are ina 
well-preserved condition, others are partially preserved, and others con- 
sist of moulds or impressions of the stipes. The specimens have been 
compressed in every possible direction, sometimes parallel to the cellulrf- 
erous face, giving the more natural expression, or that which is regarded 
as the more characteristic of the graptolite (fig. 1); others are com- 
pressed vertically to the celluliferous sides, so that the plain faces are 
pressed beyond the margins of the cellules, giving the scalariform char- 
acter (fig.3). In other specimens the pressure has been directed against 
the angles of the stipe, showing one of the plain, and one of the cellulift 
erous sides (fig. 2). The cellules in such examples extend half way across 
the width of the stipe, and show the spines upon the outer margin; while 
the spmes marking the inner margin are either compressed or broken off 
Cig. 8), leaving their bases visible along the centre of the stipe. On 
the opposite margin the mucronate spinules, marking the inner angle of 
the opposite cellules, are shown, extending outward as far as those on the 
opposite side, though that half of the stipe is entirely plain with an undu- 
lating margin between the spinules. Sometimes on this side the spinules 
may be folded beneath, and the stipe presents a continuous margin, and 
has the appearance of a uniserrate graptolite, both characters being some- 
times seen in the same individual (fig. 2). 
In specimens which are compressed vertically to the non-celluliferous 
face, the mid-rib or axis is distinctly marked, often throughout the entire 
length of the individual, as a slender filiform body. The cell-partitions in 
some specimens are well marked, but in the greater number are obscure ; 
this condition probably arising from the thick outer test of the specimen. 
The spinules originate in the smus or angle at the intersection of the lip 
of the aperture with the body of the stipe. 
