IN THE GAWILGHIJE HII>LS. 
there is no intermixture of substance. The stratum is com- 
posed of a highly indurated clay, fusible before the blow- 
pipe, into a fine black glass ; and neither it, nor the shells 
it contains, effervesce in acids. The shells are for the most 
part flattened, and belong either to the genus Conus or 
Voluta. It is not possible to conceive that so fragile a sub- 
stance as a thin land-shell should have been so completely 
flattened, v/ithout fracture, unless it had been previously 
softened by some means, which, at the same time, produced 
a sufficient degree of pressure to effect its flattening, 
I have attempted in the sketches of the shells (Plate VIIL 
fig. S, 6, 7,) to give a representation of the degree of flatten- 
ing, but I fear that it can only be well understood by ex- 
amining the specimens themselves. Neither the rock nor its 
shells effervesce in acids. Westward, the ground is covered 
by the debris of a shelly conglomerate, much more indur- 
ated and impregnated with green-earth*. Some of the shells 
are entire, but these are rarely flattened. The matrix ap- 
*pears to be siliceous, and in some cases approaches to im- 
perfect heliotrope. It is not fusible before the blowpipe. 
I may here mention, that, in a report to the Marquis of 
Hastings, in June 1819, I mentioned the existence of shells 
iii trap-rocks at Medcondah, at a height of 2000 feet abov^ 
the sea. The hill was composed of nodular trap; and lying 
-oh its surface were numerous pieces of siliceous stone, con- 
taining shells of the genera Turbo and Cyclostoma. The 
specific gravity of the stone varied from 2 to 2.5. The 
shells did not effervesce in acids, although some of them 
preserve their external polish. Internally, some of the 
stones appeared to pass into flint, particularly those of small 
specific gravity, whilst their external surface effervesced in 
• Exhibiting cavities and ishells in relief. From the shape of the 
former, there can be no doubt of their having once contained shells 
