EXPLANATION OF PLATE 56. 
91 
coast of Northumberland. This fragment is about 
five feet high, and two feet three inches in diameter 
at Its base.*' Scale one-twenty-fourth, (Sopwitli.) 
2. Fragment of the bark on the trunk of a Sigillaria, 
from Earl Fitzwilliam’s coal mine at Elsikar, near 
Rotherham. In this mine many large trunks are 
seen inclined in all directions, and some nearly ver- 
tical. (See V. I. p. 470, Note.) The bark is converted 
into a thin lamina of coal, and remains attached to 
the lower portion of this specimen. It exhibits on 
its outer surface scars formed by the articulations 
of the bases of leaves ; these are penetrated near 
their centre by three apertures for vessels that 
passed from each leaf into the trunk. The decorti- 
cated upper part of this specimen presents an im- 
pression of its striated internal surface, and exhibits 
beneath each scale two oblong parallel apertures, 
through which the vessels from a leaf penetrated 
the trunk. Scale one-half. (Original.) 
The substance of the trunk must have been in 
a state of decay, before the mud, which is now har- 
dened into shale, could have entered the interior of 
the bark. When trunks of this kind are inclined 
at an angle exceeding 45°, they are usually dis- 
tended with sandstone, or sandy shale ; when at a 
less angle than 45°, they are most commonly com- 
pressed, and have only a thin flat portion of shale, 
formed of indurated mud within their bark. The 
bark, wherever it has not perished, is converted to 
coal. 
• Articulating leaf-scar on the exterior of the bark of 
another large trunk of Sigillaria from Elsecar. Nat. 
Ad. Brongniart found a stem of Sigillaria iu a coal mine at 
ui Westphalia, which was dichotomous near its top. 
