144 Geological Society :— 
above high-water mark, above which beds of Millstone Grit would 
be brought down. ‘This accords with observed facts. On the 
Somersetshire bank the beds brought down below high-water mark 
are Mountain Limestone 770 feet, Upper Limestone Shales 330 feet. 
According to this estimate there would be 270 feet of Upper Lime- 
stone Shales above high-water mark, which would thus leave little 
or no room for Millstone Grit to be brought down to the surface.’ 
Nor has the author succeeded in finding any sign of this rock on the 
Somersetshire side. : 
Owing to the fact that softer Upper Limestone Shales are brought 
down by the fault, its westward extension may be traced by a line 
of depression resulting from the greater erosion of these softer beds. 
In the map which the author exhibited, a triangular wedge of 
Upper Limestone Shales, brought down by the fault, had its apex 
near Hill Farm (see Survey Map), and its base abutting on the 
Triassic beds south of Durdham Down. If the fault do not tend to 
die out westwards, the apex of this triangle must be placed further 
S.W., for which there is no evidence, while there is some against it. 
The southern side of the triangle marks the line of fault. Further 
west the author believed that evidence exists of the faulting-down 
of a wedge of Mountain Limestone into the Lower Limestone 
Shales. 
2. “On the Recent Discovery of Pteraspidian Fish in the Upper 
Silurian Rocks of North America.” By Prof. E. W.Claypole, B.A., - 
B.Sc., Lond., F.G.8. 
3. “On some West-Indian Phosphate Deposits.” By George 
Hughes, Esq., F.C.S.. (Communicated by W. T. Blanford, Esq., 
LL.D., F.R.S., Sec. G.S.) 
Some West-Indian specimens of phosphates were exhibited, in 
reference to which the author called attention to a description by 
Dana of an instance in which the carbonate of lime in fragments 
of coral was partially converted into phosphate, and also to the 
apparent alteration of limestone rock into phosphate of lime in 
Barbuda Island by the action of water draining a guano-like deposit 
of bats’ dung in a cave. A specimen of the phosphate of lime thus 
produced was exhibited. 
In Aruba Island the process of conversion of coral-rock into 
phosphate of lime has been in operation on so extensive a scale that 
the deposit is being largely worked for shipment. The alteration is 
probably due to the action of water containing soluble phosphates 
derived from the excrements of sea-birds (guano). Of this guano 
no trace remains ; but the fragments of coral in the underlying rock 
have been altered into a substance containing from 78 to 80 per cent. 
of phosphate of lime; and the deposit, as shipped, contains 35-7 per 
cent. of phosphoric acid, equal to 77-9 per cent. of tribasic phosphate. 
Reference was also made to some other West-Indian phosphate- 
