PLATE 27, 28. 
in general, the specimens are spar, filled with ironstone. 
The outside Is covered with*a thin, black substance, which 
appears to have been the epidermis, or outer covering in the 
recent shell, 
P. 28 — Fig. 5. A piece of the solid stratum — The shells, 
spar. This ston^ is of a deep, rich brown, when recent 
from the quarry, as represented — exposed to the air the sur- 
face becomes yellow — It takes a beautiful polish — The 
stratimi is about a foot thick, and lies, as I am informed, 
eight or nine yards below the surface. 
p. 21 FIG. 3. 
A mutilated specimen of a bivalve shell found in iron- 
stone. Spar, the outside coloured with ochre. This fossil 
differs from the shells, which are most common in the 
stone; but its imperfect state prevents the species from 
being determined. 
P. 21 FIG. 4. 
Represents a specimen of a very remarkable kind of cal- 
careous ironstone, found immediately above, and attached 
to, the solid stratum containing the shells. It consists of a 
mass of stone, which breaks into perpendicular, conical 
bodies, similar to the figure. These are made up of smaller, 
concentric cones ; in their perpendicular and diagonal frac- 
K 
