l)r Daubeny on the Geology of Sicily. £55 
the bulk of the subjacent rock. Here, in addition to the pre- 
ceding genera of shells, the sandstone contains specimens of the 
conus, buccinum, troehus, turbo, and mya. 
I must own, that some farther examination may be required 
to establish the identity of the breccia found upon the hills in 
the interior of the island, with that on the coast between Tre- 
pani and Selinus; but as I have seen the latter resting near 
Mazzara, on a rock decidedly the same with that on which the 
former is incumbent, and as the character of the rock, as well 
as its imbedded fossils, appear to coincide, I think myself war- 
ranted, for the present, in setting down the one as a continuation 
of the other. 
Let us now consider the characters of the subjacent stratum, 
which, in point of extent, is by far the most considerable in Sicily. 
Indeed, it might be safely said, that nearly half the surface of 
the island is constituted of this and the subordinate beds, as it 
extends from the neighbourhood of Palermo and Termini on 
the north, to Terra Nuovo on the south, occupies nearly the 
whole of the centre, and extends on the east to the skirts of 
Etna. The predominating rock in this formation is a bluish 
plastic clay, with which are associated beds of gypsum, of blue 
limestone, of a dark-brown slaty marl, of a white argillaceous 
limestone frequently alternating with marl, and of a brecciated 
calcareous rock, with oval masses of a white compact limestone, 
like that which occurs in the Palermo rock. 
The blue clay rarely contains shells, and the only ones I dis- 
covered in a state sufficiently distinct to be made out, were a 
mytilus and a cardium. I never recollect to have seen it rest- 
ing on any of the other beds which I have mentioned as being 
associated with it ; in every instance it appeared to be the fun- 
damental rock. 
The beds of gypsum found incumbent upon it rank among 
the most striking features in the geology of Sicily. They are 
composed sometimes of gypsum, sometimes of entire masses of 
selenite, which exhibit a confused crystallisation. Plates may 
sometimes be detached nearly a foot in length, and six or eight 
inches in breadth *. 
* The arrow-headed variety of crystals seemed the most common. 
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