THE SHELL STRUCTUEE 33 



ill size, as in Nodosa ri a ; curved, as in Mavginulina ; 

 or coiled, as in Botalia. 



The shell is, as it were, moulded upon the 

 sarcode of the organism, and when we can obtain 

 a cast of the shell — and this often happens in the 

 case of the fossil Foraminifera — we have a perfect 

 representation of the form of the animal (figs. 

 18, 19). 



This feature of continuous segmentation of the 



Fig. 19. — Anomalina ammonoides (Eeuss), Upper Chalk, 



After Eley. 



a, Shell ; h, internal cast. Highly magnified. 



bod}' in the Foraminifera gave rise to the term Pohj- 

 tlnddDiia (manj-'chambered), which was applied to this 

 section of the order by Schultze. It will be seen subse- 

 (juently (Chap. A".) how the early observers were misled 

 by the external form of the Foraminifera, which, in 

 spiral shells, such as Cristellaria and Fohjstomelhi, 

 resemble those of cephalopods, as Nautilus SLudS^dni/a, 

 except that they are much more minute. The inter- 

 nal appearances of the shells of the two groups are, 



I) 



