THE CARBONIFEROUS OF NORTHUMBERLAND. 751 
Kast Woodburn. ‘The limestone occurs in thin courses, separated by 
bands of calcareous shale, and is remarkable for the great quantity 
of well-preserved Polyzoa to be found in it. It is somewhat 
flagey, having a tendency to split up into flakes, and the faces are 
crowded with specimens of Fenestelle, Ceriopore, Leda attenuata, 
Orthoceratites, &e. The limestone is sometimes known as the ‘‘ Brigg 
Limestone,” and is associated with a thin coal which has been worked 
from time to time, but only in a very small way. Both limestone 
and coal are in the Lower Bernician, or lower part of the Carbo- 
niferous Limestone series, not very far below the Ridsdale Ironstone 
shale. 
EXPLANATION OF PLATE XXXVII. 
Fig. 1. Lepidodiscus Lebourt, Sladen: magnified 34 diameters. 
2. The same: nat. size. 
3. Diagrammatic representation of the wedge-shaped plates of the rays, 
much enlarged. 
4. The simple broad plates on the marginal portion of a ray, much 
enlarged. 
