Ch. VI.] 
SICILY VAL DI NOTO. 
67 
formed in shallower water, and nearer the action of superficial 
currents, than the superincumbent limestone, which was evi- 
dently accumulated in a sea of considerable depth. If we 
adopt this view, we must suppose a considerable subsidence of 
the bed of the sea, subsequent to the deposition of the arena- 
ceous beds in the Val di Noto. 
Blue marl with shells (c, diagram No. 5) . — Under the sandy 
beds, last mentioned, is found an argillaceous deposit of variable 
thickness, called Creta in Sicily, It resembles the blue marl 
of the Subapennine hills, and, like it, encloses fossil shells and 
corals in a beautiful state of preservation. Of these I collected 
a great abundance from the clay, on the south side of the 
harbour of Syracuse, and twenty species in the environs of 
Caltanisetta, all of which, with three exceptions, M. Deshayes 
was able to identify with recent species *. From similar blue 
marl, alternating with yellow sand, at Caltagirone, at an eleva- 
tion of about five hundred feet above the level of the sea, I 
obtained forty species of shells, of which all but six were recog- 
nized as identical with recent species f. The position of this 
argillaceous formation is well seen at Castrogiovanni and Gir- 
genti, as represented in the sections, diagram No. 5. In both, 
of these localities, the limestone of the Val di Noto re-appears, 
passing downwards into a calcareous sandstone, below which is 
a shelly blue clay. 
Strata beneath the blue marl. — The clay rests, in both loca- 
lities, on an older series of white and blue marls, probably 
belonging to the tertiary period, but of which I was unable to 
determine the age, having procured from it no organic remains 
save the skeletons of fish which I found in the white thinly- 
laminated marls J. 
* See list of these shells, Appendix II. 
f See Appendix II. 
j 1 found these fossil fish in great abundance on the road, half a mile north- 
west of lladusa, on the road to Castrogiovanni, where the marls are fetid, and 
ne.ar Castrogiovanni in gypseous marls, at the mile-stone No. 88, and between that 
and No. 89. Lord Northampton has since presented to the Geological Society 
f 2 
