THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. II. 



No. VIIL — AUGUST, 1905. 



(D:RX(3rXi<rj^ji, -A-iaTicXiES. 



I. — The Eecknt Geological History of the Baltio. 



Part II : The Ancylus Sea and the Baltic Breach. 



By Sir H. H. Howorth, F.R.S., F.G.S. 



(PLATE XIX.) 



N the previous paper I ventured to trace the history of the Baltic 

 back to the time when the latest of its raised beaches were laid 

 down, and to show that it was then considerably larger in size, and 

 that its waters were more salt than they are now, although they were 

 even then brackish (see Map I, PL XIX). 



This conclusion was derived mainly from an examination of the 

 molluscan remains in the more recent shell-beds. It is confirmed 

 by other evidence ; thus, Munthe mentions the occurrence in the 

 so-called Litorina beds of three species of Rhizopods, whose present 

 and former distribution in the Baltic is shown in the following 

 table : — 



Present In Litorina 



Distribution. Strata. 



Nonionina depressula Wamemiinde N.W. of Neder KaKx. 



Polystomella striatopunctura Warnemiiude Hernon and Gansvik. 



Rotalina Beccarii Great Belt and the ^ 



Sound S. of Hven ... Aland, Knutsboda, Obbnas, 

 35 km. S.W.of Helsingfors. 



The specimens of these three species from the Litorina deposits 

 seem, says Munthe, to be dwarf forms, and their distribution, like 

 that of the before-mentioned marine organisms, point to difierent 

 hydrographic conditions from the present (Geol. Inst. Upsala, 

 vol. ii, p. 36). 



Our present ignorance of the distribution of the Ostracoda in the 

 Eastern Baltic prevents our making the same minute induction in 

 regard to them, but Munthe says that in general the fossil Ostra- 

 codan fauna also points to different hydrographical conditions from 

 the present (id., p. 38). 



decade v. — TOL. II. — NO. VIII. 22 



