Ch. VI.] SICILY VAL Dl 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 Crcta 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 war/.-- 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. 



I 1 found these fossil fish in great abundance on the road, half a mile north- 

 west of liadusa, on the road to Castrogiovannij where the marls are fetid, and 

 near 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 



