FORAMINIFERA AND RADIOLARIA. 



95 



PLATE XVI. 

 Fio. 1. 



FIG. 2 



VARIOUS FORMS OF FORAMINIFERA (Original). 



Fig. 1. Cycloclypeus, showing external surface, and vertical and horizontal sections. 



2. Operculina, laid open to show its internal structure : a, marginal core., seen in cross section 

 at a' ; b, 6, external walls of the chambers; c, c, cavities of the chambers; c' c'. their alar prolonga- 

 tions; d, d, septa, divided at d' d' and at d", so as to lay open the interseptal canals, the general 

 distribution of which is seen in the septa e, e ; the lines radiating from e, e, point to the secondary 

 pores; g, g, non-tubular columns. 



3. Calcarina, laid open to show its internal structure : a, chambered portion ; 6, intermediate 

 skeleton; c, one of the radiating prolongations proceeding from it, with extensions of the canal- 



