304 G. Stefanini — Outline of the Geological History of 



upper Eocene) the Aquitanian rests on the lower Oligocene 

 beds, and although the transgression may not alwaj-sbe marked 

 by an angular unconformity, it is in general evident because of 

 the nature of the basal beds — conglomerate or "breccioles" 

 with littoral fossils, and often formed of debris of reworked 

 fossils from the underlying formations. 



In Friuli, on the contrary, it is the Langhian whose beds, 

 having at the base a transgressive conglomerate, rest at times 

 un conformably, and at others apparently conformably, on 

 middle Eocene or Cretaceous formations. In western Yenetia 

 also the sea invaded the land during the Langhian and the 

 islands around Yerona were submerged. 



It was thus during the two sub-periods which form the lower 

 Miocene that the transgression became complete and the sea 

 probably attained its maximum extent. This probably coin- 

 cides with the time of greatest depth — namely the upper Lan- 

 ghian. 



The Fauna. 



The fauna which invaded the Yenetian area with the Mio- 

 cene trangression is a warm sea fauna. This is evident in the 

 Aquitanian and in the lower Langhian, but especially in the 

 Tortonian, — that is to say in the stages which are represented 

 by the most littoral facies. The molluscan fauna of the Tor- 

 tonian is a truly tropical fauna, extremely rich in Terebras, 

 Cones, Mitras, Ficules, Cerithiums, Melanias, Turritellas, Cardi- 

 tas. Areas, Aviculas, etc., which both by their development and 

 by the extraordinary thickness of their shells, indicate a warm 

 climate, and waters rich in carbonate of lime. And, likewise, 

 the remains of plants and terrestrial vertebrates, which the 

 rivers carried into the sea, though rather rare, are an indica- 

 tion of a similar climate; they show that the coasts were then 

 covered with forests of pines and palm-trees,* inhabited by 

 Rhinoceros, Dinotherium, Mastodons, Tragulids, etc. 



But to return to the marine fauna : in addition to the ideas 

 which they give us of the conditions of the climate, they prove 

 also that broad and easy communications then existed between 

 the Preadriatic gulf and the rest of the Mediterranean Basin, 

 which in turn had broad connections with the oceans. Indeed, 

 it is in these latter, and particularly along the shore of Sene- 

 gal and of the Gulf of Mexico, that one finds recent faunas 

 which show the closest affinities to those which lived in the 

 Miocene Mediterranean, compared to which the fauna of the 



*E. g. Sabal, confined to America in the existing flora and reaching its 

 northern limit of range in North Carolina, occurred in Europe in the lower 

 Miocene a distance of at least ten degrees farther north and thrived through- 

 out the whole Alpine area. 



