Br. F. Oswald — Trias and Carboniferous, Caucasus. 559 



moderately deep, not shallow water, and generally below the actual 

 mud-line of the coastal margin. 



From geological evidence dei'ived from other sources it is quite 

 reasonable to assume that these glauconite grains in the clays, which 

 by the way are worn and otherwise ill-defined, have been derived 

 from local, disintegrated and re-sorted, moderately deep-water deposits, 

 such as are seen in the Barton and Bracklesham Beds themselves. In 

 the Plateau Gravels of the London Basin, by way of illustration, 

 glauconite grains are frequent ; but no one would venture to assert 

 that these granules were actually formed in the deposit, since much 

 of the material in places was derived from the Lower Greensand 

 ridges to the south. 



The difficulty of accounting for the presence of mollusca and sharks' 

 teeth in the closely associated sediments may be met in this way. 

 A slight lowering of the estuarine series would convert the area into 

 sandy and clayey submerged marine coastal plains, on which such 

 genera as Corbula, TelUyia, Leda, Area, Qlycimeris, Anomia, Cardium, 

 and Cardita could flourish ; whilst slightly deeper conditions would 

 permit of the existence of genera like Panopcea. At the same time 

 the fact of many of the mollusca found in this series being in the 

 state of casts, shows that the sea-bottom at this period was in a state 

 of oscillation rather than of equilibrium. 



isTOTiOES OB^ DynEi!>/a:oii?.s. 



Trias and Cakboniferous in the Caucasus. 



"WiTTENBURG, P. W. Rcccnt Researches on the Trias of the Caucasus. 



(In Russian.) Bull. Acad. Imp. Sci. St. Petersburg, 19-12, 



p. 433. 

 Robinson, W. IST. Recent Researches on the Geological Structure of 



the Northern Caucasus in the Basins of the Rivers Bielaya and 



Laba. (In Russian.) Bull. Acad. Imp. Sci. St. Petersburg, 1913, 



p. 33. 



Translated and abridged from the Russian by Felix Oswald, 



D.Sc, F.G.S. 



rPHE discovery in 1907 of Upper Trias in the Kuban district of the 

 1 Caucasus, which was described in the Geological Magazine 

 (Dec. V, Yol. YI, No. 538, April, 1909, p. 171), has been con- 

 siderably amplified and extended by the researches of P. W. 

 Wittenburg, who explored the same district, viz. the upper courses 

 of the Little Laba and Bielaya Rivers, and his results may be con- 

 veniently summarized in tabular form : — 



1. Rhcetic Stage. — (1) Typical Avieula contorta beds on Mt. Tkhach. 



(2) Lower Rhsetic is represented by grey crinoidal limestone 

 interbedded with red marly limestone containing many Brachiopods, 

 particularly masses of Spirigera belonging to the typically Rhsetic 

 group of S. oxycolpos, Eramr., and 8. Mnnzavinii, Bittn. (Kdssen 

 Beds). It is well exposed in the Kun Yalley near Mt. Tkhach, and 



