232 ANIMALS OF THE SEA FLOOR 



recent research has proved to have a varied fauna. 

 These zones must be taken as applying primarily to 

 the shores of the North Atlantic and the Mediterranean, 

 but with some small alteration will be found to hold 

 good for many other seas. 



The Littoral Zone, or the space between high and 

 low water mark, is dealt with elsewhere in this volume 

 (Chapter III.). It is necessarily inhabited by a fauna 

 which is able to endure a certain amount of periodic 

 exposure to the air. At its lower limit it passes into 

 what is known in European waters as the Laminarian 

 Zone, taking its name from the oarweed or Tangle 

 (Laminaria), which, with other seaweeds, is its most 

 striking feature. It extends to a variable depth, 

 usually less than 15 fathoms. Though the name 

 Laminarian is somewhat restricted in its application, 

 yet the physical characters of this zone may be recog- 

 nized almost universally. These may be summed up 

 as the penetration of sunlight, and the consequent 

 presence of abundant vegetable life in the form of 

 brown and red seaweeds ; the exposure to violent wave 

 action which may stir up sediment, and the lowered 

 salinity from the surface drainage of the land even in 

 the absence of any large rivers. It is in this zone 

 that we must look for the majority of the vegetable 

 feeders of the sea, with the exception of those which 

 live upon minute floating diatoms and similar organisms 

 of the Plankton. 



Below the region in which the brown seaweeds 

 flourish, or (speaking very roughly) from 15 fathoms 

 downwards, lies the region which we now deal with 

 comprehensively as the Continental Shelf. 



As a general rule the land-masses of the globe are 

 surrounded by an area of comparatively shallow water, 

 varying in extent, which has been called the " area of 



