FORAMINIFERA. 



I II 



the walls of the shell, or simply by the mouth of the latter, or by both 

 these sets of apertures combined. 



From a palasontological point of view the only part of a Foram- 

 inifer with which we have to deal is the shell or " test," and there 

 are several points to notice in this connection. Firstly, as regards 

 the actual composition of the shell, it is in the majority of cases cal- 

 careous, or composed of carbonate of lime, but it is rarely chitinous, 

 and it is not uncommonly " arenaceous " — that is, composed of 



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Fig. 18.— A many-chambered Foraminifer (Rotalia venetd) with the radiating and netted 

 pseudopodia protruded. Greatly magnified. (After Max Schultze.) 



particles of sand cemented together by some animal substance or 

 by carbonate of lime. With the horny or chitinous Foraminifera 

 (Gromidtz) we have nothing to do here, as they have never been, 

 and are never likely to be, detected in a fossil condition. 



