164 



THREE CRUISES OF THE "BLAKE.' 



lata (Fig. 496), is frequently brought up in the globigeriua 



ooze from depths greater than 400 fathoms. 



The group dates back to the Jurassic, and 



seems to be a characteristic deep-sea type in 



all the oceanic basins. Ammodiscus tennis 



(Fig. 497), taken by 

 the "Challenger" off 

 New York in 1,300 

 fathoms, is a recent rep- 

 resentative of a very common palaeozoic 

 type of the carboniferous period. 



According to Brady, Cyclammina (Fig. 

 498) represents in our seas the highest 

 type of arenaceous foraminifers. The 

 genus is characterized by the labyrinthian 



structure of the test (Fig. 499), and is abundant in depths 



below 100 fathoms in the West Indian region. 



Fig. 497- Ammodiscus 

 tenuis. L . (Brady.) 



Fig. 498. 



Fig. 499. 



Cyclammina cancellata. (Brady.) 



Most variable in the shape and structure of their shells are 

 the Textularinse. A very common type 

 of the group is the cosmopolitan 7V.r- 

 hilaria sagittula (Fig. 500), which at- 

 tains a length of 6 mm. ; it has been 

 dredged in the Atlantic in 2,675 fath- 

 oms. Another abundant form, which 

 dates back to the cretaceous, is the com- 

 pact and thick-walled 7\ trochus (Figs. 



Fig. 500. Textuiaria sagit- 

 tuia. Y- ( G e 8 -) 



