lut 

 trs 



SHALLOW-WATER FAUNA. 23 



Ocean the mud is almost entirely composed of 

 Kadiolarian shells, and is then called " Kadio- 

 larian ooze": and in the Southern Sea a mud 

 called Diatom ooze has been found, which con- 

 sists principally of the siliceous shells of these 

 minute algae. Notwithstanding these varieties 

 of the mud, and others that space does not allow 

 me to refer to at length, we may suppose that 



"the floor of any one of the great oceans were 

 posed it would have the appearance to a 



-raveller of a vast desert-like expanse, without 

 a stone, a rock, or a cliff to vary the monotony 

 of the scene. At one time it was supposed to 

 be an absolute plain, without any important 

 change of level from the mud line of one con- 

 tinental coast to the other; but the result of 

 modern submarine explorations has been to prove 

 that in all the great ocean-basins, hills and ridges, 

 as well as troughs and deep holes occur, which 

 break the monotony of the generally smooth and 

 level character of the bottom. 



CHAPTER II. 



SHALLOW-WATER FAUNA. 



IAVING considered thus briefly the general con- 

 ditions under which the animals of the sea must 

 live, we may now consider more in detail the 

 special conditions of shallow-water life. 



In water of only a few fathoms in depth, the 

 direct light of the sun is capable of reaching and 

 influencing all living things that occur, either at 



