Vol. 60.] EOCENE, ETC. SURROUNDING THE DARDANELLES. 265 



130 feet above sea-level, containing Neritina fluviatilis ( = danu- 

 bialis), Didacna crassa, Dreissensia polymorpha, and Mytilus eduhs. 

 This beach commemorates the last high-water mark of the Ponto- 

 Caspian closed basin, and probably followed a portion of the contour 

 of the Marmora lake at the time when the Gallipoli shell-bank 

 accumulated (fig. 6, p. 2(34). 



The conglomerate-rock, upon which Gallipoli is built, consists in 

 great part of shells of Didacna crassa, Dreissensia Tschaudce, and 

 Dr. polymorpha. The deposit is not, in nry opinion, a raised beach, 

 and it is about double the height generally stated. It is spread 

 out over at least 2 square miles, with a fairly-uniform surface 

 about 80 feet above the water. At Bas-Chesme Bay (Gallipoli), the 

 conglomerate is partly replaced by a local bed of sandy loam, in 

 which is a seam, about a foot thick, of the same Caspian shells 

 {Didacna crassa and Dreissensia polymorpha), evidently in or close 

 to their original location, as many of the shells have both valves 

 connected. 



Prof. Andrussov considers the Gallipoli Conglomerate to be the 

 equivalent of the Tschauda Beds at Kertch, containing Dreissensia 

 polymorpha, Dr. Tschauda?, Cardium crassum, C. Cazecos, and 

 C. Tsehawli. which he shows to be an Upper Pliocene fauna of 

 Caspian type, deposited in an enclosed brackish lake before the 

 Dardanelles were in existence (24, xxx, Table of Beds above the 

 Sarmatic, facing p. 4 ; and 26). 



VIII. Pleistocene. 



According to Prof. Philippson's researches (14, p. 138), the 

 deep depressions in the iEgean district, due to tectonic collapses, 

 began to take shape between the Lower and the Upper Pliocene. 

 I propose to show that the consequent reversal of the 

 drainage of the Dardanelles area resulted in the 

 formation of a river, the watershed of which lay 

 south-west of Gallipoli, and that when this was worn down 

 by subaerial agencies to the level of the dammed-in Pontic water, 

 the following rapid outflow caused the formation of the Dardanelles 

 channel. 



The first result of the tectonic changes referred to b}- Prof. 

 Philippson would be to convert the Xorth ^Egean area into a large 

 closed basin, bounded on the south by the chain of the Xorthern 

 Cyclades, Andros, Tinos, Mykoni, Xikaria, and Samos. The dip 

 of the Sarmatic strata from the Dardanelles south-westward 

 shows that there was considerable relative subsidence in this 

 direction, as the level of the Upper Sarmatic of Imbros is now 

 some 600 feet lower than that of the corresponding beds east 

 of Chanak in the Dardanelles, in a horizontal distance of about 

 25 miles. The Sarmatic deposits of Tenedos show a similar dip. 

 This settlement, on the verge of the JEgean depression, is further 

 indicated by an ancient river-channel, discovered by Mr. Calvert, 

 which has cut through the neck of land at Maitos (fig. 7, p. 264) 

 opposite Chanak, to within 100 feet of the present water-level. 



Q.J.G. S. Xo. 239. i 



