Ch. VI.] SICILY VAL DI NOTO. 65 



The shells in the limestone are often very indistinct, some- 

 times nothing but casts remaining, but in many localities, 

 especially where there is a slight intermixture of volcanic sand, 

 they are more entire, and, as we have already stated, can almost 

 all be identified with recent Mediterranean testacea. Several 

 species of the genus Pecten, are exceedingly numerous, par- 

 ticularly the large scallop (P. Jacobceus)) now so common on 

 the coasts of Sicily. The shells which I collected from this 

 limestone at Syracuse, Villasmonde, Militello (V. di Noto), and 

 Girgenti, have been examined by M. Deshayes, and found 

 to be all referrible to species now living, with three or four 

 exceptions*. 



The mineral characters of this great calcareous formation 

 vary considerably in different parts of the island. In the south, 

 near the town of Noto, the rock puts on the compactness, 

 together with the spheroidal concretionary structure of some of 

 the Italian travertins. At the same place, also, it contains the 

 leaves of plants and reeds, as if a stream of freshwater, charged 

 with carbonate of lime and terrestrial vegetable remains, had 

 entered the sea in the neighbourhood. At Spaccaforno, and 

 other places in the south of Sicily, a similar compact variety of 

 the limestone occurs, where it is for the most part pure white, 

 often very thick bedded, and occasionally without any lines of 

 stratification. This hard white rock is often four or five hun- 

 dred feet in thickness, and appears to contain no fossil shells. 

 It has much the appearance of having been precipitated from 

 the waters of mineral springs, such as frequently rise up at the 

 bottom of the sea in the volcanic regions of the Mediterranean . 

 As these springs give out an equal quantity of mineral matter 

 at all seasons, they are much more likely to give rise to unstra- 

 tified masses, than a river which is swoln and charged with 



* For lists of these see Appendix II. I procured at Villasmonde, seven species ; 

 at Militello, ten j in the limestone of Girgenti, of which the ancient temples are 

 built, ten species ; from the limestone and subjacent clay at Syracuse, twenty-six 

 species ; in the limestone and clay near Palermo, also belonging to the newer Pli- 

 ocene formation, one hundred shells. 



VOL. III. F 



