SUPPLEMENT. 
513 
Fig. 7. 
It is still possible that it may have assumed another form in its original mode of 
growth, and that these small bifurcate fronds are but the separated offshoots from 
a rhizoma which extended along the muddy bottom of the sea, giving off at intervals 
the ascending stipes in pairs, which in their progress became branched as before 
shown ; and in this case, the little transverse bar in the bending of the frond is a 
part of the broken rhizoma. 
Geological position and locality. In the shales of the Hudson-river group : Near 
Albany. 
Graptolithus divaricate (n. s.). 
Stipe bifurcate from the radicle : branches slender, widely diverging, 
divergence from 90 to 120 degrees, very slightly increasing in width 
from the base, serrated on the lower side ; serratures nearly straight 
on the outer margin, with the apices of the denticles somewhat rounded; 
the indentation rounded at the bottom, extending across one-half the 
width of the stipe; margins of the indentations thickened : the margin 
opposite the serratures is not thickened. 
Surface marked by a row of small nodes placed obliquely to the direction 
of the axis, and situated just below and a little on one side of the 
bottom of the serrature. Serratures 22 - 26 in the space of an inch. 
This species somewhat resembles in its general form, when the stipes are widely 
divergent, the G. serratulus; but the serratures are on the lower instead of the upper 
margin of the stipe, and are quite different in form and proportions. The small nodes 
or tubercles are, alsoj so far as known, a distinguishing feature. In this species these 
nodes are distinctly oval in form, and have a depression or slit in the summit; and 
[ Palaeontology III.] 65 
