of the Thracian Bosphorus. 391 



without fossils. The stratification is in general horizontal, a character com- 

 mon to nearly all the tertiary formations, which I saw in Turkey. 



That portion of this deposit which occurs near Constantinople appears to 

 have been accumulated in an estuary. The most abundant shell is an oval, sub- 

 triangular bivalve, apparently a Mactra, which composes almost the entire 

 substance of some of the beds; there is also a ribbed bivalve resembling a 

 Cardium. These are apparently the only fossils which belonged to marine 

 genera, all the rest having been natives either of the land or of fresh water. 



Potamides, 1 species. 



Neritina, I species, the delicate black stripes 



remaining. 

 Ctjclostoma, 1 species. 

 Helix, a species like H. pomatia. 

 , a species resembling H. rufescens. 



Bulinus, resembling B. montanus. 



, similar to B. acutus. 



Clausilia, 1 species. 

 Pupa, 1 species. 

 Planorhis, like P. alba. 

 Cypris, 1 species. 



The terrestrial shells are remarkable for their near approach to existing 

 forms. They are less generally diffused than the marine and fresh-water 

 species, but are abundant in the quarries at Makri-keui. 



A single specimen of a bone occurred in this formation, but it is too im- 

 perfect for me to decide, whether it belongs to a mammifer or to a reptile. 



I found no traces of a tertiary deposit along the banks of the Bosphorus, 

 whence it may be inferred that this channel has been opened at a compara- 

 tively late period. Tertiary beds are said to exist along the shores of the 

 Euxine; and lignite has been worked for fuel at Domouz-deri, a few miles 

 west of the Bosphorus. 



4. Ancient Alluvium. 



A few miles north of Constantinople are some extensive deposits of clay, 

 sand, and gravel, reposing on the Silurian schist. The latter formation is 

 barren and devoid of trees, but the alluvial clay favours the growth of the 

 oak and causes the forest of Belgrade. These deposits are of great thick- 

 ness and consist chiefly of ferruginous clay, with pebbles and bowlders of 

 quartzose and sandstone rocks interspersed. The general want of stratifi- 

 cation and the rounded form of the bowlders, denote an aqueous action of 

 considerable violence. These accumulations of detritus appear to skirt the 

 southern side of the Lesser Balcan range towards the N.W. 



Taken as a whole, the deposits bear a close analogy to those which in Eng- 

 land have been called diluvium ; and they appear to have resulted from causes 

 acting on a greater scale than any of those, which produced the local alluvia, 

 noticed by me in Asia Minor. 



November, 1836. 



