158 NEWER PLIOCENE STRATA OF SICILY. [Ch. XIIL 



and, after being traced for hundreds of yards, are again found at a cor- 

 responding height on the opposite side of the valley. 



The corals are usually branched, but not by the division of the animals 

 as some have supposed, but by the attachment of young individuals to 

 the sides of the older ones ; and we must understand this mode of in- 

 crease, in order to appreciate the time which was required for the building 

 up of the whole bed of coral during the growth of many successive gen- 

 erations.* 



Among the other fossil shells met with in these Sicilian strata, which 

 still continue to abound in the Mediterranean, no shell is more conspic- 

 uous, from its size and frequent occurrence, than the great scallop, Pecten 

 jacobaws (see fig. 129), now so common in the neighboring seas. We 

 see this shell in the calcareous beds at Palermo in great numbers, in the 

 limestone at Girgenti, and in that which alternates with volcanic rocks in 

 the country between Syracuse and Vizzini, often at great heights above 

 the sea. 



Fig. 129. 



Pecten Jacob cent ; half natural size. 



The more we reflect on the preponderating number of these recent shells, 

 the more we are surprised at the great thickness, solidity, and height 

 above the sea of the rocky masses in which they are entombed, and the 

 vast amount of geograj>hical change which has taken place since their 

 origin. It must be remembered that, before they began to emerge, the 

 uppermost strata of the whole must have been deposited under water. 

 In order, therefore, to form a just conception of their antiquity, we must 

 first examine singly the innumerable minute parts of which the whole is 

 made up, the successive beds of shells, corals, volcanic ashes, conglomer- 

 ates, and sheets of lava ; and we must afterwards contemplate the time 



* I am indebted to Mr. Lonsdale for the details above given respecting the 

 structure of this coral 



