THE PELAGIC FAUNA AND FLORA. 



195 



the Tortugas, where numerous patches of them gave a reddish 

 color to the sea. 



The siliceous types of Polycistinse (Fig. 120), so common in 

 former geological times in the West Indies, form an extensive 

 deposit at the Barbados,^ near the highest part of the island, 

 are now found but rarely in the Atlantic. A few types of the 



■ ) 



Fig. 120. — Pterocanhim charvtcleum. Highly 

 magnified. (Miiller.) 



Fig. 122. — Sphserozoum. V^ , 



Thalassicolse (Fig. 121), and Acanthometridse, as well as of 

 such forms as Collozoum and Sphserozoum (Fig. 122), are, how- 

 ever, quite common in the Gulf of Mexico and Caribbean, and 

 during the summer come as far north as the larger pelagic 

 animals. Siliceous radiolarians are quite common in the tropi- 

 cal regions of the Pacific. 



While many of the foraminifera, like Globigerina and Has- 



^ Nummulitic beds occur in Thibet at a height of sixteen thousand feet. 



