264 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



lowest known sedimentary stratum) may be the equivalent of the 

 trias, that opinion cannot be adopted without some fossil e\idences. 

 Whilst the mainland is void of palaeozoic rocks, they exist however 

 in Sardinia, where they were discovered by General della INIarmora. 

 These rocks prove by their fossils to be true Silurian limestones and 

 schists*. In Sardinia, deposits with species of palaeozoic coal plants 

 also occur, but unluckily the political troubles of Italy prevented my 

 examination of these rocks. General della Marmora has, however, 

 left no spot of the island unsurveyed, and having made a beautiful 

 topographical map of it, he will soon complete his important work, 

 and inform us whether the coal deposits of that island, like those of 

 Oporto described by Mr. Sharpe, are associated with the Silurian rocks, 

 or are of subsequent age. The existence of Lower Silurian rocks in 

 Portugal, as recently made known to us by Mr. Sharpef — the preva- 

 lence of Devonian fossils in tlie north of Spain, and the presence of 

 both Silurian and Devonian strata in Morocco J, where they were 

 first recognised by M. Coquand — their persistence along the African 

 Atlas and their reappearance near Constantinople, are data sufficient 

 to enable us to picture to ourselves a vast girdle of palaeozoic rocks 

 of which the Alps and the Pyrenees formed the northern and the 

 north-western limits, and which, ha^dng been elevated from beneath 

 the sea at a very ancient period, have constituted the shores of a large 

 IMediterranean in which the secondary and tertiary rocks of Italy 

 have since been accumulated. In this sense, Sardinia may perhaps 

 be only viewed as a detached island in this ancient basin. 



Excluding from our present consideration the eruptive rocks, whe- 

 ther plutonic or volcanic, which have perforated the subsoil of Italy 

 in so many places, and not now alluding to certain ancient crystalline 

 rocks of Calabria and Sicily, it may be said that the chief mineral 

 masses of the peninsula in ascending order are — 1st, limestones and 

 schists ; 2ndly, hard sandstones and impure limestones often compact ; 

 and 3rdly, marls, sands and conglomerates. The lowest of these 

 great lithological groups embraces in some regions both the Jurassic 

 and cretaceous systems ; the second or arenaceous group represents 

 in given countries both the upper cretaceous and that which I have 

 shown to be the eocene of the Alps ; whilst the third contains the 

 miocene, pliocene, and other overlying strata. To this general litho- 



* General della Marmora kindly sent to me a collection of those fossils, inclu- 

 ding orthoceratites and graptolites. These were examined and partially named 

 by M. de Verneuil, to whom I transmitted them ; but having lost that memoran- 

 dum, M'hich was forwarded to me in Italy, I subsequently referred these fossils to 

 Mr. Sharpe, who is satisfied that they belong to the Lower Silurian group. In 

 addition to orthoceratites, graptolites, crinoids, &c., Mr. Sharpe recognises eight 

 or nine species of Orthis, among the best-preserved of which are the Ort his patera 

 (Salter, MSS.), common near Bala, and O. Lusitanica (Sharpe), of the Lower Si- 

 lurian rocks of Vallongo near Oporto, closely related to the b.flabelluhim, Sow. 

 Sil. Syst. The Spirifer terebratuUformis (M'Coy) also occurs, — a species of the 

 Lower Silurian rocks of Cumberland and Ireland. 



t See Journ. Geol. Soc. Lond, vol. v. p. 142, and pi. 6. fig. 5 (llussia in Europe 

 and Ural ^Mountains, Map of), 



J For the Devonian rocks of the Asturias see Paillette's memoir, Bull. Soc. Geol. 

 de France, vol. ii. p. 439, and for the palaeozoic rocks of Morocco see id. vol. iv. 

 p. 1188. 



