SUPPLEMENT. 
515 
Graptolithus marcidus. 
Fig. 1. A specimen more contracted than usual, with the serratures obtuse. 
Fig. 2. An individual presenting a more expanded form, with distinct den¬ 
ticles at the lower extremity and a minute radicle below. 
Fig. 3. A young form where the serratures are not developed, or are flattened 
in the line of their direction, and in which the minute fibres or ra¬ 
dicles at the base are well preserved. The specific relations of these 
forms have not been fully determined; and I am, at present, unable 
to refer them to any other than this one» 
2 13 
Geological position and locality. In the shales of the Hudson-river group : Near 
Albany. 
Graptolithus angustifolius (n. s ). 
Stipes simple, linear, slender, biserrate : serratures well defined, the 
denticles short ovate-acute, the extremities sometimes subobtuse ; base 
marked by minute setiform radicles; midrib projecting beyond the 
serrated portion in a capilliform extension. Serratures arranged in the 
proportion of about twenty-eight to thirty in the space of an inch. 
This species has a narrow stipe with very distinct denticles, which are usually 
closely arranged or apparently overlapping each other at the base, while sometimes 
they are separated more distinctly and the indentation deeper. The form and pro¬ 
portions of these denticles are different from those of any species of Graptolite in 
the collections from these shales, and often more resembling the minute denticula- 
tions on the fronds of fossil ferns than those of the graptolites. The denticles are 
often subalternate on the opposite sides of the stipe, and frequently variable in the 
same individual. 
The accompanying figures illustrate the usual characters of this species. 
\ 
Fig. 1. A single stipe, twice the natural size; 
Fig. 2. A portion still farther enlarged. 
This species is associated in the same laminae of slate with G. 
marcidus , G. whitjieldi, G. spinulosus, and Reteograptus geini- 
tzianus . 
1 2 
Geological position and locality. In the shales of the Hudson-river group : Near 
Albany. 
