440 



DISTRIBUTION IN SPACE AND TIME 



burrow in the sand; and Turbellarian Worms (Turbellaria), 

 variously shaped flattened forms often seen adhering to stones 

 or other objects. 



N critic Hedgehog- Skinned A nimals ( Echinodermata ). In 

 warmer seas, and to some extent in our own, Feather-Stars 

 (Comatula] climb or swim in shallow water. Ordinary Star- 

 Fishes (Asteroidea) use their numerous tube-feet for creeping, 

 and Brittle- Stars (Ophiuroidea) progress on the sea- floor by 



Fig. 1293. Section through part of a Coral Reef 



means of their snake-like arms. Sea- Urchins (Echinoidea) creep 

 slowly about after the fashion of star-fishes, and their tube-feet 

 adhere so strongly to rock-surfaces that some of them can even 

 withstand the surf of coral-reefs. The Sea-Cucumbers (Holo- 

 thuroidea) of shallow water either creep or burrow. 



Neritic Zoophytes (Ccelenterata). On British coasts the 

 solitary Sea-Anemones, often beautifully coloured, are the most 

 noticeable of the Sea- Flowers (Anthozoa). The fauna of the Great 

 Barrier Reef of Australia includes some creatures of this kind 

 which are as much as 2 feet in diameter when fully expanded. 

 In some of the warmer seas, where the water is sufficiently clear, 



