THE GEOLOGY OF LONDON. 
5 
brick- and tile-yards, but perhaps the most noted locality in 
London is at Highgate Archway, where Mr. Wetherell obtained 
a valuable series of fossils. To an ordinary observer it would 
not appear by any means a fossiliferous deposit, as the fossils 
occur in particular bands or zones, and are not very often dis- 
played in the clay-pits. Sheppey is one of the best localities 
for fossils, and it has yielded a number of fossil fruits which 
were described, many years ago, by Dr. Bowerbank. The 
London clay is indeed very rich in fossils — crabs and lobsters, 
mollusca, fish, turtles, crocodiles, and a few mammals. Pro- 
fessor Owen remarks that the number of species of turtles 
obtained from Sheppey exceeds that of the species of Chelone 
now known to exist throughout the globe. 
The most remarkable fossil, however, of the London clay, 
obtained also at Sheppey, was recently described by Professor 
Owen. It is the skull of a bird, consisting of the brain-case, 
with the basal portion of both jaws, the alveolar margins of 
which are produced into bony teeth. This bird he named 
Odontopteryx , and from a consideration of its characters, he 
concluded that it was web-footed and a fish-eater, and that in 
the catching of its slippery prey it was assisted by the arm. - 
ture of its jaws. 
The nature of the London clay, according to Mr. Prestwich, 
indicates a tranquil deposit of no great depth. The fauna, 
taken altogether, he considers to indicate a moderate rather 
than a tropical climate ; and yet the flora is, so far as can be 
judged, certainly tropical in its affinities. 
Besting in isolated patches upon the London clay, and form- 
ing conspicuous hills whence some of the finest views near 
London are to be obtained, is a deposit of fine mealy sand 
called the Bagshot sand, about 100 feet in thickness. This is 
found at Harrow, Hampstead Heath, Highgate, High Beech, 
and Brentwood. In Essex the sand is overlain by pebble-beds 
of rolled flints. They are undoubtedly marine deposits, formed 
in shallow water. Fossils are exceedingly scarce, a few casts of 
shells having alone been found. 
The beds to which we have now alluded may all be con- 
sidered conformable, that is to say, they lie evenly and regularly 
one upon the other ; although, as we have mentioned, the 
Oldhaven beds die out over the northern part of the London 
area. We have no evidence of any deposit immediately 
following the Bagshot beds in this district. In the Isle of 
Wight we find them succeeded by beds containing freshwater 
shells, as at Headon Hill and Whiteeliff Bay. While these 
deposits were forming, and undoubtedly during the succeeding 
miocene period (which was characterised by a higher temperature 
in Europe, extending even as far as Greenland, where the fig, 
