﻿68 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 18, 



fact, they have for their uppermost limit a red limestone, sometimes 

 schistose, sometimes arenaceous, which underlies the neocomian lime- 

 stone, and which often rises to considerable elevations, covering with 

 its more or less inclined strata the beds of compact red limestone 

 which are always inferior to it. The red limestones of the second 

 group are usually separated ; the beds of the one alternating with the 

 beds of the white or yellowish neocomian limestone, which contain 

 the same fossils ; while the invariably thin strata of the other are 

 sometimes red, sometimes grey, and represent the Flysch of the Swiss, 

 the Macigno of the Tuscans, and also, according to you, the Carpa- 

 thian sandstone ; in a word, they represent the Scaglia of the Vene- 

 tian geologists, with which (in the descending order) the chalk for- 

 mation begins. I shall only occupy myself at present with the first 

 two limestones of which I have spoken above, which although till 

 now they have been confused together under the single name of red 

 ammonitic limestone, deserve however, as you will see, to be distin- 

 guished from one another. 



As regards the geographical distribution of the ammonitic lime- 

 stone, Baron von Buch observes, that it forms a most extensive zone, 

 which touches the Crimea on the one side, and Mount Tatra in Poland 

 on the other, and which extends to the west as far as the French 

 Jura. He afterwards mentions that the Ammonites Tatricus, Pusch, 

 the Terehratula diphya, Buch, and some species of Aptychus, are the 

 fossils which more particularly characterize this formation. In Italy 

 the same rock is in like manner prolonged through an extensive tract 

 of country ; it begins near the confines of the German Tyrol (Stua 

 in the district of Cortina d'Ampezzo), throwing out its branches to 

 the foot of the Dolomitic Alps of Agorda (Celo, Colazzo, &c), and 

 stretching in various directions ; towards the west it extends into the 

 district of Feltre (Cesio, Fastro, not far from Arsie), and advances 

 into the Setti Comuni (Rotzo, Castelletto, Cesuna) and into the 

 Veronese territory (le Sine) ; and towards the east it extends above 

 Belluno (Igne, Pirago, Lavazzo, &c.) where it is quarried for build- 

 ing-stone. In Lombardy it reappears under the same conditions 

 (Arbe, Suello, Trescorre, Entratico), but from thence it does not 

 spread into Piedmont ; whereas in Tuscany, Umbria, Modena, and 

 Liguria, it constitutes a well-marked formation. In fact, the com- 

 pact red ammonitic limestone lying under the red schistose limestone 

 of Parodi, described by Pilla, and that of the territory of Perugia, 

 and of the whole length of the Spoleto mountains, are both charac- 

 terized by the same fossils which we have collected in a long succes- 

 sion of years in the mountains of Lombardy and Venice, and which, 

 with the exception of a few species, do not differ from the fossils con- 

 tained in the red limestones of Liguria. 



Epiolitic Red Limestones of the Upper Jurassic group. 



This group, in those places where it has acquired its full deve- 

 lopment, rises in extensive mountains, of a nearly constant form, 

 presenting slopes more or less steep on one side, especially in the 

 upper third part of their height, and forming on the opposite side 



