1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 2/3 



experiences, in handling this part of the subject in such a region. At 

 Nice indeed the succession is clearly shown from neocomian lime- 

 stone, through greensand and chalk, up to overlying nummulitic 

 strata ; but in the whole of the tract east and west of Genoa, the slaty, 

 hard, calcareous flagstones (alberese) and the macigno sandstones are 

 grouped together as a higher member of the secondary series. In fol- 

 lowing the northern edges of the great plain of Piedmont, a wall of 

 crystalline and eruptive rock subtends the alluvial plains of the Po ; 

 and though some representatives of cretaceous rocks flank the Alps and 

 rest upon Jurassic limestones to the north of Milan and near Como, 

 I shall not now speak of these, because I have not visited them. 



Good types of the cretaceous rocks of the north of Italy occur, 

 however, in that outlier of the Alps with which I am acquainted, 

 the Euganean hills. Separated from the chain by the trough of the 

 lower tertiary deposits of the Vicentine, these hills, long known to 

 consist chiefly of eruptive trachytes and scaglia, or the equivalent of 

 the chalk, have, thanks to their vicinity to the abode of scientific men 

 at Padua, been at length well developed. In his elaborate work, full 

 of lithological and mineral description and views concerning the 

 pseudo-volcanic operations of the region, M. Da Rio has also the merit 

 of having enumerated, with the assistance of Professor Catullo and 

 others^ a certain number of fossils*. But these were not so described 

 or grouped as to furnish to any extent geological divisions in the 

 secondary rocks, though on the whole the strata containing Ammo- 

 nites, Belemnites, and certain Echini {Ananchytes ovatus) were sepa- 

 rated from the strata loaded with nummulites, which, in following 

 Brongniart, M. da Rio considered to be tertiary. The more recent 

 researches of Pasini and Catullo, and particularly those of De li^igno, 

 show that the calcareous masses, formerly known under the terms of 

 grey, white and red scaglia, are divisible into formations by their fos- 

 sils ; the lowest of these representing the Oxfordian or *' ammoni- 

 tico rosso" of the Alps, with Ammonites Hommairi (D'Orb.), A. 

 biplex (Sow), and A. Zignoamis (D'Orb.). The next or neocomian, 

 forming the base of the cretaceous system, is characterized by the Crio- 

 ceras Duvaliiy Belemnites dilatatus (Blainv.), Ammonites cryptoceras 

 (D'Orb.), A. Astierianus (D'Orb.), and A. infundibulum (D'Orb.). 

 The next overlying stage is considered to be the "Aptien," D'Orb., 

 and contains the Hippurites neocomiensis, with Spherulites and Am- 

 monites Guettardi. The uppermost band is the scaglia, or true 

 equivalent of the white chalk, with Inoceramus Lamarckii, Ananchytes 

 tubercidatus, Holaster, &c. 



In his description of the " Terreno-Cretaceo " of the Venetian Alps, 

 as exhibited in the Monfenera between Fener on the north and Pede- 



cision, void as they are of fossils and perforated in all directions by serpentine and 

 eruptive rocks. It may however be supposed, as suggested in the text, that a part 

 of them may be cretaceous, and a part, on the parallel of strata which elsewhere 

 contain nummulites. The same species of fucoids ranging throughout the eocene 

 of the Alps down into the lower chalk of Northern Italy, are no criteria of age. 



* Orittologia Euganea del Nobile Niccolo da Rio, Padova, 1836, with a coloured 

 map and a lithographic profile. 



