Cxiv PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



marked character between the chalk and the portion of the Paris 

 Basin in which Nummuhtes occur. On the Mediterranean, how- 

 ever, such is not the case, as the mineral deposits of succeeding 

 formations appear to blend into each other in such a manner 

 that no geological difference would be suspected were it not for 

 the appearance of characteristic fossils. Signor Cocchi, for ex- 

 ample, describing the upper portion of the cretaceous formation, 

 notices the Calcaire Alberese, a compact limestone of very fine 

 grain and of a yellowish colour, though frequently varied by the 

 presence of foreign substances, and often exhibiting a zone-like dis- 

 position of colours. In the south of Tuscany this limestone is 

 replaced by another equally compact but more argillaceous, and 

 coloured a greyish blue, like the neck of a pigeon. Both these 

 limestones have been deported in thin and almost schistose beds, 

 and neither has afforded other fossils than Fucoids. In the Cam- 

 pigliese and the Isle of Elba, a powerful series of beds of a very fine- 

 grained limestone occurs, the colour of which is sometimes rose, 

 sometimes glaucous green, and sometimes pure white ; the fracture 

 is largely conchoidal and numerous dendritic crystallizations are 

 highly characteristic. This deposit is largely developed in the 

 Apennines ; but all who have visited the Mediterranean must at once 

 recognize in this description the familiar characters of the white 

 limestone, such, for example, as it is seen at Corfu and elsewhere ; 

 but, as I found it often difficult at the latter place to draw a line be- 

 tween deposits of different ages, though succeeding each other with- 

 out a mineral change, so also Signor Cocchi remarks that the same 

 lithological forms being repeated above the nummulitic limestone, 

 as were found below it, it is impossible to separate them from each 

 other when the nummulitic deposit is deficient. 



Proceeding to the Tertiary formations, Signor Cocchi observes, 

 that the lower or Eocene member consists almost entirely of the 

 Macigno and Upper Calcaire Alberese ; and then, subdividing it into 

 two sections, he states that the nummulitic limestone, so well de- 

 scribed by Murchison, forms the basis of the system, and constitutes 

 the only satisfactory horizon between the Cretaceous and Tertiaiy 

 formations, as it is almost impossible to draw a line of distinction 

 between them in its absence. To the hard, compact, and granular 

 nummulitic limestone, succeed argillo-calcareous schists and lime- 

 stones with flints, so that Signor Cocchi remarks, that the series of 

 deposits here brought within the region of the Tertiaries by the 

 intercalation amongst them of the nummulitic limestone is a simple 

 repetition of the mineral deposits, the Calcaire alberese and Pietra 

 columbina, of the Upper Cretaceous rocks. The characteristic fossil 

 is the Nemertilites Strozzii (Savi and Menegh.), a gigantic marine 

 worm. The Macigno, which is in its normal condition a quartzose 

 grit with calcareous cement, is next described in all its varieties, 

 some of which are very interesting, more especially the prismatic, in 

 which the rock breaks up into rhomboidal prisms. Signor Cocchi 

 observes, that it was during the deposition of the Macigno that the 



