160 



THREE CRUISES OF THE " BLAKE.' 



Norway, Bear Island, and Spitzbergen, Biloculina rinyens forms 

 the most important organic constituent of the bottom deposits, 

 and Pourtales and Sars have named this the Biloculina clay ; 

 but this term is hardly to be understood in the same sense in 

 which we speak of globigerina ooze, the Biloculinse forming- 

 but a very small proportion of the ooze deposit. (Fig. 485.) 



Fig. 485. Biloculina tenera. With expanded pseudopodia. 7 T 5 . (Sclraltze.) 



Orbiculina adunca (Fig. 486) is a very common deep-water 

 form ; it attains a diameter of 6 mm. In both Orbiculina and 



Fig. 487 



Fig. 48G. 



Orbiculina adunca. (Brady.) 



its ally, Orbitolites, the young of the disk-like foraminifer is 

 nautiloid (Fig. 487) ; but as the chambers of the adult increase 



