1848. j MURCHISON ON THE STRUCTURE OF THE ALPS. 263 



logical arrangement there are, however, local exceptions of consider- 

 able extent. In many tracts, also, the absence or extreme rarity of 

 fossils, and the rapid undulations and frequent breaks in the strata, 

 render it very difficult closely to identify each rock-formation \^dth 

 its equivalent in other parts of Europe. This last remark applies 

 chiefly to the rocks of Jurassic and cretaceous age ; for the great 

 masses of the hard sandstone or macigno, particularly where it is 

 associated with nummulites, are unquestionably supracretaceous or 

 eocene ; whilst each of the younger deposits which overlie them is 

 easily referable, both by order of superposition and abundant organic 

 remains, to its respective place in the tertiary series. 



In his recently published general geological map of Italy and its ad- 

 jacent isles, jNI. Collegno having inserted the Silurian rocks of Sardinia 

 as the lowest known sedimentary deposit, attempts two divisions 

 only of all the rock masses of the peninsula beneath the miocene. 

 The lowest of these, from the verrucano conglomerate upwards to 

 the Oxfordian Jura, is coloured as Jurassic ; whilst all the overh^ing 

 strata, whether they represent the neocomian, upper greensand and 

 chalk, together with the nummulitic limestones and macigno, are 

 classed together as cretaceous. It will be readily understood, from what 

 has been said of the Alps, that I m^ust object to the arbitrary union 

 of the two last-mentioned masses mth the cretaceous rocks ; and 

 hence one of my chief objects will be to show, that in Italy, as in the 

 Alps, the nummulitic and upper macigno group is also of eocene age. 

 I shall further indicate the existence of a natural succession from the 

 top of the eocene or bottom of the miocene up into the pliocene, 

 wherein the fossils exhibit a zoological transition into the latter period. 

 But before I enter on these prominent points of this part of the me- 

 moir, I will first say a few words on the Jurassic rocks, which are the 

 oldest in which organic remains have been discovered in the penin- 

 sula, and then give a brief sketch of the true cretaceous rocks which 

 succeed to them. 



The best key to an acquaintance with the lowest strata containing 

 organic remains, with which I am acquainted, is that which is ex- 

 hibited in the promontories of the gulf of La Spezia and the ad- 

 jacent parallel ridges of the Apuan Alps. This tract has long been 

 known to English and French geologists by the able description of 

 Sir Henry De la Beche, published many years ago, and to Italians 

 by a memoir of M. Guidoni*. Even at the time when he wrote. Sir 

 H. De la Beche suggested, that the fossils found on the west side of 

 the bay were probably of oolitic or Jurassic age, though from their 

 peculiar characters and the supposed presence among them of ortho- 

 ceratites and goniatites (the latter being then called ammonites of the 

 coal-fields), he very properly left the question somewhat open. But 

 since then, additional collections and a rigid examination of the or- 

 ganic remains have settled the question. The supposed small ortho- 

 ceratites are found to be simply the alveoli of belemnites, and the 

 ammonites, though not occurring in England, belong to forms known 

 in the Jurassic series of Southern Europe. Grouping the observa- 

 tions of his contemporaries, and adding fresh data of his own, the 

 * See Trans. Geol. Soc. Fr. 1«'<' ser. vol. i. p. 23, and Giornale Ligustico, 1828. 



