FOSSILIFEROUS NODULES. 45 
of pyrite. Polished specimens of the shelly exterior of the nodule show 
that it contains a tendency to lamination in the arrangement of its more 
or less altered fragments, the larger and flatter edges or faces of these 
being approximately concentric with the surface of the nodule. Possibly 
this apparently quite local laminated or fibrous structure is referable to 
chemical alterations proceeding pari passu with mechanical and concre- 
tionary movements during solidification of the vein stuff. 
Perhaps the most interesting thing about these nodules is that they 
contain remains of organisms. A polished portion of the rock revealed 
fragments of plants, as shown in figure 15. The three upper fossils are 
of black material, while the two lower forms are yellowish brown. in 
color. The latter may be seed cases, 
while those above appear to be termi- 
nals or bud-like extremities. Sir J. W. 
Dawson, to whom a drawing of the 
most perfect specimen was submitted, 
wrote that it was too small to deter- 
mine. While the black streaks seen 
in other fract ures of the vein mate- 
rial in proximity to these nodules in- 
dicate the presence of more fossils, the 
writer has as yet been unable to find 
anything determinable. 
The plant fragments figured do not 
occur in any individual bits of rock in the matrix of the vein, but evi- 
dently got into position among the rock fragments as bits of dead or 
living plants that were washed or fell into the gaping fissure during the 
process of filling. They are remnants of the vegetation of the period in 
which the clay-veins were made. 
Ficure 15.—Fossils from Nodules in Clay-vein. 
Magnified 5 times. 
OTHER CHARACTERISTICS 
The clay-veins as proved and surveyed over about 2,000 acres of mine 
workings in the Pittsburg seam, about 27 miles south of Pittsburg, Penn- 
sylvania, and bordering the Youghiogheny river, are observed to have 
no reference to or connection with (1) the dip of the coal field; (2) the 
axes of the anticlines and synclines or the “basins” running through 
the district; (3) the “cleat” of the coal; (4) the general trend of the 
“slack-veins ” (these veins are referred to further on in this paper) ; (5) 
the local ‘‘swamps” or “hills” (depressions and elevations of the coal 
seams, irrespective of the main anticlines, etcetera); (6) the present 
