4 E HERON-ALLEN AND A. EARLAND ON THE FORAMTNIFERA 



Since the time of Ehrenberg there have been other discoveries 

 of Cambrian Foraminifera in America (6) (7) and Siberia (8). 

 We have not had an opportunity of seeing either of these reports, 

 but it may be noted that the New Brunswick rocks furnished 

 representatives of the pelagic genera Orbulina and Globigerina 

 (family Globigerinidae), while the Siberian rock is described as 

 assuming an oolitic structure on account of the numerous Fora- 

 minifera which it contains. It is therefore apparent that the 

 Foraminifera had already assumed that dominant position which 

 they have ever since maintained in the biology of the sea. 



Turning to our own country, the oldest Foraminifera yet 

 recorded are those described by Chapman (9) from a limestone 

 of Upper Cambrian age near Malvern (PI. 1, fig. 1). This record is 

 'of great interest because all the Foraminifera described are either 

 monothalamous (genera Lagena, SpiriUina) or polythalamous 

 shells of simple type (genera Nodosaria, Marginulina, Cristel- 

 laria). As will be seen from the rock section figured by Chapman, 

 the Foraminifera of one genus, SpiriUina, form a considerable 

 proportion of the entire mass of the rock (PI. 1, fig. 1). The other 

 species described are stated to have been of very rare occurrence. 

 Now SpiriUina is one of the simplest conceivable types of rhizo- 

 podal shell structure, an undivided tube coiled on itself in one plane, 

 iand is theoretically one of the forms which might be expected 

 to turn up in the earliest records. Chapman has on certain 

 minor points of structure instituted a new species {SpiriUina 

 Groomii Chapman) for this Cambrian type, but it appears to 

 be nothing more than a variety of SpiriUina vivipara Ehrenberg, 

 a species which at the present day occurs on muddy bottoms 

 of moderate depth in all parts of the world.* So far as we 

 are aware, however, there is no other record of its occurrence 

 in sufficient abundance to form a noticeable constituent of any 

 deposit, recent or fossil. In recent dredgings it cannot be 

 described as an abundant species. 



In the next period, the Silurian, there are many records (10) 

 (11) (12) (13) of Foraminifera, but they do not appear to be 

 numerous. Brady (12) records and figures four species of the 



* Since this was written specimens resembling SpiriUina Groomii (Chap- 

 man) have been found in dredgings made in Blacksod Bay, Co. Mayo, and 

 also in the Moray Firth. They will be described and figured in the 

 forthcoming report on the Foraminifera of the Clare Island Survey. 



