SUPPLEMENT. 



.119 



Genus Tiiamxograptls ( 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. 



These bodies are associated with the GraptoUtes; 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. Tlie 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. 



Tlianinograptus 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.l. 



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 



