GRAPTOLITES. 53 
found to be at the epoch of the Quebec group. Several genera and a 
few species are known in the Trenton formation; and a greater develop- 
ment, embracing most of the genera and many species, occurs at the 
period of the Hudson River formation in Canada and the United States. 
In the Clinton strata we have a single species of Graptolithus, and a Retio- 
lites ; while Dictyonema and Jnocaulis occur in the Niagara beds. In 
all the subsequent geological formations we have found no true graptolites, 
and the only representatives of the family consist of fragments of Dictyo- 
nema, belonging to a few species. ‘These occur in the Upper Helderberg 
and Hamilton formations, above which we do not yet know a species of 
any genus referable to this family of fossils. The genus Graptolithus 
has its upper limit in the shales of the Clinton formation, and all others of 
the family, except Dictyonema, are restricted to the Silurian system. — 
The geographical distribution of the Graptolitide is not in all respects 
coincident with the extent of the geological formations. Dendrograptus 
occurs in the Potsdam sandstone of the St. Croix valley; but neither 
this nor any other graptolite is known in other localities of the sand- 
stone, so far as I am-aware. ‘The species of the Quebec group, number- 
ing more than all the other formations together, have been identified 
for a longitudinal extent of about 900 miles; Point Lévis, Orleans Island, 
St. Anne’s River (Gaspé), and the western part of Newfoundland, being the 
principal localities. But although the Quebec group is known to extend 
into Vermont and along the eastern counties of New-York, I am not 
aware that graptolites have been found in any authentic localities of that 
formation.* Thus far, therefore, these fossils of the group are known 
only in Canada and Newfoundland. 
The Trenton limestone, while furnishing two species of Graptolithus in 
New-York, gives at the west no specimens of the genus proper; but we 
have one Dictyonema, a Buthograptus, and an Oldhamia?t im the same 
formation in Wisconsin, though not elsewhere known. 
The Utica slate at Utica abounds in the remains of graptolites, and 
these fossils are of frequent occurrence at Oxtungo Creek, in the valley 
of the Mohawk. It is probable that some of the localities referred to the 
Hudson River formation, may be in the Utica slate, which, owing to the 
disturbed condition of the strata, is not separable from the succeeding 
slates. 
In the Hudson River formation, the characteristic graptolites, of numerous 
species, have been found, in greater numbers than elsewhere, at Norman’s 
Kill near Albany ; but they occur at Stuyvesant’s Landing, and at the 
* A single branching form, the G. Milesi, has been published in the Geological Re- 
port of Vermont. The specimen was found in a boulder of slate, but it is probably of 
the Quebec group. [ 
D 
