328 
THE GEOLOGIST, 
K.E. 
2 
3 
•I 
3 
Section of the Oyster-deposit • at Sunderidge. The figures refer to the table of strata at page 327. 
Of the shells which enter into the formation of this conglomerate, the 
great bulk are oysters, many specimens of which are found with the 
valves closed, others with them open, whilst multitudes of single valves 
abound, a few covered with Vermilia and Serpula on both surfaces, and 
exhibiting also perforations of Clionidae. The interior of most of the 
closed oysters is occupied by a lining of carbonate of lime, from one to 
three or four lines in thickness, leaving a central cavity ; the internal 
surface of which is studded with very small dog-toothed crystals of 
calcareous spar. This phenomenon I noticed also in many angular 
cavities in the rock itself, alongside of other imbedded shells. Many of the 
oysters resembled the common edible species of the present day, whilst 
others were thick and massive with a large and wide hinge ; some of the 
latter I measured 5| inches long, and 4j wide. Many specimens were 
adherent to a single pebble, three or four commonly, and the mass 
which I have already referred to had six perfect oysters attached to a 
large pebble, besides about nine different valves of dead specimens 
adherent to the pebble and to one another. On the upper valve of one 
of the perfect oysters, four young ones, about half an inch wide, are 
attached, and quite perfect, a circumstance which especially points 
to their having grown on the spot. Nevertheless, I would infer that 
