THE DEEP SEA ANIMALS 1 89 



the sea bottom beyond the coastal muds is formed of globig- 

 erina ooze, consisting of the shells of minute shelled animals, 

 the oceanic foraminifera, largely globigerinas, with some bot- 

 tom living types and a few other things. Less common are the 

 pteropod oozes, made up of the shells of oceanic molluscs, the 

 radiolarian oozes, and the diatom oozes. Toward the middle 

 of the oceans the oozes gradually pass into an excessively line 

 red mud, which is the typical bottom of all the abysses far 

 from land. 



On the red mud everywhere and sometimes on the oozes 

 lie scattered the ear-bones of whales and the teeth of sharks, 

 the only portions of these animals that will persist indefinitely. 

 Some of the sharks' teeth on the red mud are of gigantic size, 

 several inches in length, and came from species long extinct. 

 On the ear-bones and the teeth manganese slowly collects, in 

 time enclosing them in characteristic nodules of various sizes. 

 As over the red mud oceanic life is so scanty as to be practi- 

 cally non-existent, these nodules for the most part probably 

 represent the remains of decrepit sharks and whales which 

 have strayed out here and died. 



Below the twilight zone the variety of animal life rapidly 

 lessens, and, on account of the uniformity of conditions in all 

 oceans at these levels, becomes practically the same every- 

 where. 



The basic food here consists of detritus from the plants 

 along the shores, decreasing rapidly in amount with distance 

 from the land, and a correspondingly increasing amount of 

 organic matter derived from the bodies of the creatures in the 

 layers above which, dying, sink gradually to the bottom where 

 further decay is arrested by the perpetual cold and the great 

 pressure which prevent, or at least inhibit, the action of bac- 

 teria. The foraminifera, pteropods, diatoms, etc., and the 

 sargassum and other floating sea-weeds dying and going to the 

 bottom carry there at least a portion of their organic substance, 

 which mixes with the mud. This bottom ooze or mud when 

 brought on deck seems absolutely clean, but in the warm air it 



