any where, and the existing helices (thickly strewed over the soil
formed by the calcareous tufa, and found very sparingly on the fig-
trees in the sandy plain),iwere specifically distinct from the considerably
smaller ones, forming entire masses of the loose sandstone
; and generically distinct from the enormous species imbedded
in its surface6.
The flaky sandstone frequently formed isolated ledges,' or
hillocks, of a most picturesque appearance, on the southern part
of the plain, numerous flake's being regularly piled on each other,
shooting upwards from the soil in angles of 45°, and seeming
to emulate the- lofty peaks of tufa behind them, Plate 7, A f.
Imbedded in these hillocks are numerous, close-grained, indurated,
cornuform, hollow masses, with smaller lateral branches, which
I conceive to have been formed by the sand having enveloped
plants or fragments of wood, subsequently and entirely decomposed.
These sands have evidently been thrown up by the séa,
on the low southern coast of the island (almost on a level with it),
and have been gradually advanced, and propelled inland, and
afterwards more or less agglutinated, until they have reached the
northern side, enveloping the vegetation, and entombing the
e The recent shells which I found on the beach ofJPqrto Santo* were a cypr&a, a
cassidaria, of an orange-colour; three species,,of colombella, a frochus a djisky
ground, and spotted with a dull red; three, pectines, one spotted with red, another
brown, streaked with white and .rose-colour, and the shell remarkably thick in
texture, (probably a variety of the p. jlexuosus) and fig, 20, of a, palerJcolour, mam-
millated and shaded with light green; four species of venus,;one white,(lyith, brown
streaks, and a rose-coloured apex, fig. 19, a second of a pale flesh-colour? and another
of the same colour, but nearly transparent, also one of a flesh-colour with rich brown
streaks; fig. 18, the cardium edvle, a small halyotis, of a deep.red, \yith green, and
orange streaks; perhaps a variety of A. tuberculpsc^^nda rose-coìpurej eehinus,
streaked with purple, and with a brown spot at the insertion of each spine.
f According to M. Beudant, the basaltic tufas, of Tihany are cpvered.’by a sandstone
resembling the silex mólaire of the Environsof Paris.