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upper Trigonia Grit was a deposit of shells, covered up by a 
coarse grit, or occasionally a fine mud. In the latter condition 
the Shells are well preserved, and the walls and road-side stone 
heaps in the district attest their immense abundance. The 
Coral bed also contains a large number of fossils, but the 
deposition upon it of the brown Grit beds indicates a con- 
siderable change in the marine life of the Oolitic Sea. The 
Mollusea, so abundant in the Trigonia bed, for a time with- 
drew to other seas, and the brown sandy Grits are nearly . 
destitute of organic remains. 
The brown beds disclose a succession of strata differing 
somewhat in their lithological character. The lower bed is 
very tough, it contains large Oolite grains in clusters with few 
fossils. The bed next above is fine grained and nearly destitute 
of fossils. It is, perhaps, the hardest and most compact bed 
in the formation. It is succeeded by another tough Oolite 
bed, nearly the counterpart of the first in its lower portion, 
but becomes fossiliferous towards it upper surface. 
The Coral bed separates the ragstone series into two divisions, 
between which there is considerable difference, both as regards 
the structure of the rocks and the fossils they contain. For 
reference it would be convenient to call the beds above the 
Coral bed the Upper, and those below, down to the Freestones, 
the Lower Ragstones. 
The term “ pisolitic ragstone” would apply to the beds near 
the base of the Inferior Oolite. 
The upper Ragstones appear to have a wide range. In the 
Calcaire de Longwy, in the province of Luxembourg, they are 
represented, and Messrs. Cuapuis and Dewanque have figured 
from that formation numerous species also found at Rod- 
borough, including Homomya gibbosa, Lima gibbosa, Lima 
duplicata, Modiola gibbosa, and Holectypus depressus, the first 
of which does not occur m the Cotteswolds earlier than the 
beds I have described, and the others are some of the most 
abundant fossils of the Clypeus Grit. 
In his correlation of the Jurassic Rocks, before alluded to, 
Dr. Wricut mentions the stage Calcaire a Collyrites ringens 
