58 Review of the New York Geological Reports. 
the most delicate structures of its fossils, that it was accumulated 
during a period of great tranquillity. 
y reason of its soft and destructible nature, this black slate is 
seldom exposed to view, except in ravines and water-courses: 
nevertheless it has a wide range ; commencing near the Hudson 
river it runs nearly due west to Lake Erie and the west line of the 
state. ‘This rock and the Genesee slate have doubtless formed the 
impervious beds which hold up the waters, not only of that lake, 
but also of Lakes Huron and Michigan, since they show them- 
selves in many places bordering their shores. All that flat wet 
région of country interspersed with small lakes and ponds, lying 
in the vicinity of the Kankakee and the head waters of the Wa- 
bash, is also probably underlaid either by these schistose argilla- 
ceous beds themselves or the clay derived from their disinte- 
ration. 
“re the western part of New York the Marcellus shale is not 
over fifty feet thick: it thickens, however, to the eastward ; we 
are informed by Vanuxem that in his district it has been bored 
through a hundred feet in search of coal. 
- The best localities cited for examining this deposit, are, the ra- 
illage o d 
Sulphuret of iron occurs every where in connection with this 
formation ; and sulphate of barytes is not uncommon in the sep- 
taria. It contains no where valuable minerals. Owing to the 
presence of sulphuret of iron, the springs issuing from the black 
slate are often sulphuretted. 
By its decomposition a stiff, cold, clayey soil results; but for- 
ely in the state of New York it is mostly so covered with 
drift that it rarely gives character to the surface soil to any con- 
siderable extent. ; 
Fossils are not abundant in the Marcellus shales. Goneatites 
measuring sometimes one foot across, occur in the two upper 
limestone layers between the lower and upper shales. 
The forms figured in Vanuxem’s Report are given on the Op- 
posite page. 
The most characteristic fossils of this formation in the western 
part of the state are embraced in the following wood cut taken 
from Hall’s Report. 
The black slate of the Western states has usually been consid- 
ered the equivalent of the Marcellus shale; but so few fossils 
have hitherto been observed in that formation in Ohio, Indiana, 
linois, or Kentucky, and these are so obscure, that no satisfactory 
paleontological evidence has been adduced in support of this de- 
cision. Indeed some facts rather favor the idea of its being the 
