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EXPLANATION OF PLATES. 
By J. J. H. Teall, F.R.S. 
PLATE I. 
FIG. 1. PEA GRIT, INFERIOR OOLITE, STROUD, GLOUCESTERSHIRE. 
Pisolitic bodies showing irregular accretions of calcareous mud and 
organic fragments around organic nuclei, in a matrix of crystalline calcite. 
PISOLITIC AND OOLITIC LIMESTONE, CORALLINE OOLITE, STOWER, 
DORSETSHIRE. (Portion shown in quadrant.) 
The margin of some of the pisolitic bodies shows a very minute form 
of Girvanella-structure, which is somewhat more obscure in the centre. 
One organic fragment is shown. 
FIG. 2. WHITE OOLITE, UPPER FREESTONE, INFERIOR OOLITE, NAILSWORTH, 
GLOUCESTERSHIRE. 
Composed of grains showing very fine concentric and radial structure, 
in a matrix of perfectly clear crystalline calcite. 
FIG. 3. GRANULAR LIMESTONE, INFERIOR OOLITE, DOULTING, 
SOMERSETSHIRE. 
Clastic organic fragments, sometimes rounded, sometimes angular, in 
matrix of clear crystalline calcite. The secondary calcito surrounding 
the fragments is in optical continuity with that of the fragments them- 
selves, so that the structure of the rock is analogous to that of quart/.ites 
in which secondary enlargement of the original grains has taken place. 
FIG. 4. BLUE AND BROWN OOLITIC LIMESTONE, LINCOLNSHIRE LIMESTONE, 
CASTLE BYTHAM, LINCOLNSHIRE. 
Oolitic grains, showing concentric and radial structure, and pellets 
enclosing organic fragments. 
On the unweathered oolitic grains there are crusts of pyrites, which 
give the blue colour to part of the rock ; in the brown portions the 
material is limonite, as determined by Mr. A. B. Dick. The weathered 
and unweathered portions are separated by a sharp plane of division. 
FIG. 5. PISOLITIC AND SHELLY LIMESTONE, LINCOLNSHIRE LIMESTONE, 
GREYLEES QUARRY, SLEAFORD, LINCOLNSHIRE. 
Organic fragments, pellets, and compound pellets enclosing oolitic 
grains, &c. Some of the larger pellets contain three or four oolitic grains 
in a matrix of calcareous mud. 
The general matrix is crystalline calcite. There is however, between 
the coarse-grained calcite, and the outer margin of the grains and pellets, 
a narrow zone of calcite in the form of minute crystals of the dog-tooth 
spar variety ; the points projecting outwards and thus giving the 
external surface of the grains a very rough aspect. 
FIG. 6. OOLITIC AND SHELLY LIMESTONE, FOREST MARBLE, CORSHAM, 
WILTSHIRE. 
Organic fragments without oolitic incrustations ; and oolitic grains 
showing concentric and radial structure. The nuclei of the oolitic grains 
comprise amorphous calcareous matter (pellets) ; organic fragments ; and 
broken oolitic grains. The matrix is clear crystalline oalcite. 
