558 F. Chaponan — Eocene Foraminifera. 



The largest example of the Hengistbuiy Head series has a diameter 

 of -6 mm., whilst the larger of Dr. Brady's figured examples from 

 the English tidal rivers has a diameter of "4 mm. This variety is 

 exceedingly common in tlie washings. 



Fam. TEXTULAEIID^. 



Genus ViRGDLiNA, d'Orbigny. 



Virgulina suhsqiiamosa, Egger. Fig. 9. 



Virgulina stcbsquamosa, Egger, 1857, Neues Jahrb. fiir Min., etc., p. 295, 



pi. xii, figs. 19-21; Brady, 1884, Eep. Chall., vol. ix, p. 415, pi. ii, 



figs. 7-11. 



Forarainiferal tests allied to this form have already occurred in the 



estuarine deposits (Holocene) of the Fen-land in the East of England.* 



Only one small example of this species was found, having a length 



of -423 mm. 



JVote on the accompatiying Ironstone Bed. — A thin slice of the iron- 

 stone of the Hengistbury Head Beds was examined under the 

 microscope, with the following result : — 



The general character is that of a fine-grained ironstone composed 

 of excessively minute granules of carbonate of iron stained with 

 peroxide of iron. Scattered throughout the rock and occasionally 

 occurring in nests are minute angular fragments of quartz, such as 

 are met with in the finest river silts. A few obscure stem-like 

 fragments are also seen embedded. Under a high power the separate 

 granules of carbonate of iron are seen to be covered with peculiar 

 amber and ruddy-coloured articulations, probably representing the 

 residual peroxide of iron after the change from the condition of bog- 

 iron ore. 



Conditiofis of Deposition. — Some interesting facts are brought out 

 by the foregoing occurrence of the somewhat sparse and peculiar 

 foraminiferal fauna of the Hengistbury Head clays. The forms are 

 all arenaceous, showing a marked absence of calcareous rocks or 

 calciferous waters in the neighbourhood. Such a fauna is generally 

 found in the tidal estuarine areas of great rivers close to the coast 

 and having a partially landlocked character. Similar deposits would 

 occur, for example, on those parts of the Essex Flats at the present 

 day, which are occasionally flooded at especially high tides, and where, 

 in the boggy parts, saprophytic vegetation flourishes, capable of 

 extracting the carbonate of iron from the surrounding water. The 

 small dimensions of these Foraminifera, the poorly developed tests 

 with shrunken chambers, and generally starved appearance point to 

 their being a survival of a normal deep-water terrigenous facies, 

 which has been pushed into uncongenial surroundings ; for parallel 

 types of all the forms here enumerated are well known in many of 

 the green and blue muds of our deeper coastal deposits. 



Tlie question here arises, how came the glauconite grains in the 

 clay deposit if the evidence of the Foraminifera points so strongly to 

 estuarine conditions ? for glauconite seems to be, so far as known, 

 a material which is chemically deposited under marine conditions in 



^ Brady, loo. cit., p. 415. 



