30 
organic remains have been noticed in any part of these sands. In 
the lower beds a mine of quicksilver was worked profitably during 
the last century near Coina, south of the Tagus; and the gold dust 
for which the sands of that river have been so long celebrated, Mr. 
Sharpe believes, is derived also from the lower or ferruginous sands. 
(.) Almada Beds.—A complete section of this deposit is not ex- 
hibited in the neighbourhood of Lisbon, and the strata are so very 
irregular both in thickness and composition, that it is difficult to 
connect the sections displayed at different localities. ‘The strata are 
best exposed in the cliff south of the Tagus, between Trafaria and 
Almada. The whole of the series is arranged by Mr. Sharpe in 
three groups, the uppermost consisting of limestone and sands, the 
middle of blue clay, and the lowest of another series of limestones 
and sands: but Mr. Sharpe does not attach much value to the sub- 
division ; as the same fossils are found in the beds above and below 
the blue clay. The deposit constitutes a triangular tract on the 
Lisbon side of the Tagus, extending from that city to Verdelha, a 
distance of about fourteen miles ; it also caps some hills between Belem 
and Fort St. Julian. South of the Tagus, it forms the cliffs already 
mentioned; and a band which ranges from St. Ubes northwards to 
Palmella, and thence south-west to within a mile of Aldea do Meco, 
skirting the flanks of a ridge of secondary formations. A detached 
mass of the Almada beds occurs at the western end of the Serra de 
San Luiz, between St. Ubes and Azeitao, abutting unconformably 
against the elevated edges of the beds of red sandstone, and another is 
on the shore at the foot of San Felippa near St. Ubes. North of the 
Tagus, the beds incline from 5° to 10° to the south-east; but to the 
south of the river between St. Ubes and Aldea do Meco, the dip varies 
from 25° to 30°, and conforms to the position of the band with respect 
to the ridge of secondary rocks, being to the south-east between St. 
Ubes and Palmella, andto the north-west between the latter town and 
Azeitao. Thebeds of the detached mass near the western end of the Serra 
de San Luiz, dip about 30° north, and those of the mass on the shore 
at the foot of San Felippa, 80° towards the older red conglomerate, 
having been thrown over beyond the perpendicular. On the coast 
at Casilhas near Almada, the level of the strata is affected very con- 
siderably by faults. North of the Tagus a fault cuts off the tertiary 
strata at Oeiras, the Almada beds forming one bank of the stream, 
and the Hippurite limestone the opposite; but the strata of each 
deposit are horizontal. In Lisbon the Almada beds rest uncon- 
formably on the Hippurite limestone ; but between the city and Ver- 
delha, conformably on the lower tertiary conglomerate. In the band 
ranging from St. Ubes by Palmella towards Aldea do Meco, they 
repose in general also conformably on the red sandstone. The 
greatest height attained by the formation is the Castle Hill near Pal- 
mella, the summit of which is 930 feet above the level of the sea, 
and at this point two lines of disturbance meet. Fossils are very 
abundant in some of the beds, but sufficient attention has not yet 
been paid to them to permit their being compared with the organic 
remains of other tertiary districts. A long-hinged oyster, Ostrea 
