i8o 



ANIMAL LIFE OF THE DEEP SEA BOTTOM 



?(n\i}fi/nx):iy^ l()S2. 



Animals caught in the Philippine Trench at 10,000 metres, i Sea-cucumber (Scotoplanes), 

 17 millimetres. 2 Sea-cucumber (Myriotrochus), seven Tnillimetres. 3 Gullet of annelid 

 (Macellicephala), seven millimetres. 4 Bivalve (Glomus), seven millimetres. 5 Echiu- 

 roid worm (Echiuroidea), about five millimetres. 6 Amphipod (Hirondellea), three milli- 

 metres. 7 Isopod crustacean (Macrostylis), six millimetres. 



But in recent years it has gradually been realized that turbidity currents 

 must play an important part under certain conditions. If rough weather 

 whisks up clay in the sea water near the shores it is obvious that muddy 

 liquid will have a greater specific density than clear sea water, and con- 

 sequently will tend to settle in depressions of the continental shelf, in 

 earthquake fissures or old river-beds where the sea-bed has been higher, 



