SUPPLEMENT. 
519 
Genus Thamnograptus (n. g ). 
Bodies consisting of straight or flexuous stipes (simple or conjoined at 
base ?), with alternating and widely diverging branches : branches 
long, simple or ramose, in the same manner as the stipe. Substance 
fibrous or striate; the main stipe and branches marked by a longitu¬ 
dinal central depressed line, indicating the axis. Cellules or serratures 
unknown. 
X 
These bodies are associated with the Graptolites; and from a general similarity- 
in their substance, I suppose them to belong to the same family of fossils. In all the 
specimens the surface visible is smooth or striated without indentations, and marked 
by cross fractures or cleavage planes. The fragments of what appear to be carbonized 
plants, in the shales of the Hudson-river group, probably all belong to this genus, 
or to the Dendrograptus. 
ThamnogTaptiis typus (n. s ). 
Stipe strong, flattened : branches alternating, about half as wide as the 
main stipe and expanding at their junction with it, simple, marked 
along the centre by a depressed line or axis. Surface marked by fine 
longitudinal striae, with obliquely transverse fractures or lines of 
cleavage. 
Fig. 1. 
The accompanying figure is from a fragment 
of this species, of the natural size. 
Geological position and locality. In the shales 
of the Hudson-river group : Near Albany. 
Thamnograptus typus. 
This genus was proposed by me in 1858, in a paper read before the American 
Association for the Advancement of Science; but no publication has been made of 
