66 NfcWER PLIOCENE PERIOD. [Ch. VI. 



sedimentary matter of different kinds, and in unequal quan- 

 tities, at particular seasons of the year. 



The great limestone,, above mentioned, prevails not only in 

 the Val di Noto, but reappears in the centre of the island, 

 capping the hill of Castrogiovanni, at the height of three thou- 

 sand feet above the level of the sea. It is cavernous there, as 

 at Sortino and Syracuse, and contains fossil shells and casts of 

 shells of the same species*. 



Schistose and arenaceous limestone, fyc. (b, diagram No. 5). 

 The limestone above-mentioned passes downwards into a white 

 calcareous sand, which has sometimes a tendency to an oolitic 

 and pisolitic structure, analogous to that which we have described 

 when speaking of the travertin of Tivolif. At Floridia, near 

 Syracuse, it contains a sufficient number of small calcareous 

 pebbles to constitute a conglomerate, where also beds of sandy 

 limestone are associated, replete with numerous fragments of 

 shells, and much resembling, in structure, the English corn- 

 brash. A diagonal lamination is often observable in the cal- 

 careous sandy beds analogous to that represented in the first 

 volume (chap. xiv. diagram No. 6), and to that exhibited in 

 many sections of the English crag, to which we shall after- 

 wards allude. 



In some parts of the island this sandy calcareous division, b y 

 seems to be represented by yellow sand, exactly resembling 

 that so frequently superimposed on the blue shelly marl of the 

 Subapennines in the Italian peninsula. Thus, near Gram- 

 michele, on the road to Caltagirone, beds of incoherent yellow 

 sand, several hundred feet in thickness, with occasional layers 

 of shells, repose upon the blue shelly marl of Caltagirone. 



When we consider the arenaceous character of this forma- 

 tion, the disposition of the laminae, and the broken shells some- 

 times imbedded in it, it is difficult not to suspect that it was 



* Dr. Daubeny correctly identified the Val di Noto limestone of Syracuse with 

 that of the summit of Castrogiovanni. Jameson, Ed. Phil. Journ., No.xxv.p. 107, 

 July, 1825. 



f Vol. i. chap. xii. 



