THE BENTHAL 189 



Fishes of varied origin are provided with a rostrum with which they 

 can plow the sand in search of prey. Belone, 7 with its elongate lower 

 jaw extending beyond the upper, roots out the Ammodytes and an- 

 nelids, and the halfbeaks (Hemiramphidae), 8 and Pegasidae feed in 

 the same way. The sawfishes, Pristis and Pristiophorus , with trans- 

 verse teeth on their "saws," are said to dig up the bottom to secure 

 their food. 



The smaller fishes of this littoral formation lead a precarious life. 

 They are attacked from the air by terns and gulls and from the deeper 

 water by larger fishes. Fundulus, one of the most common genera to 

 be found along the Atlantic coast, commonly lives in shallow water; 

 there, as the tide comes in, e.g., along the coast of the Carolinas, it 

 follows its advance in over the sand, rooting in the newly covered 

 sandy bottom for food. It continues with the advancing tide and often 

 enters pools which retain the water for some time without holding it 

 until the next tide. In such places, when the tide begins to ebb, the min- 

 nows apparently test their line of retreat from time to time and return 

 to feed along the bottom with their fellows. In a long series of observa- 

 tions, Mast failed to find any Fundulus stranded in these sandy tide 

 pools. When he dammed the outlet to such a pool, the fishes collected 

 in aggregations near the old outlet and, individually or in groups, 

 passed out of the pool over the damp sand to the retreating sea water. 

 He found that they could climb a ridge 10 cm. high and travel over 

 land for 3 m. 9 



The size of the particles composing the bottom has an important 

 effect on its inhabitants. Gravel and pebble beach is found only in 

 strongly moving water, close to the water's edge; this biotope is quite 

 azoic, since the movement of the stones on each other destroys all life. 

 Coarse sand is poorer in animal life than fine. Muddy bottom is rich 

 in life, but mud mixed with sand is still more so. 



This region of the sandy depositing shore is a climax formation 

 comparable with the beech and maple community on land. The eco- 

 logical processes here are in approximate equilibrium, and neither 

 organisms nor physical forces are changing the environment with 

 rapidity. Of course, there may be deposits of sand which tend gradually 

 to raise the shore line and so cause the whole complex to move further 

 out to sea; but the community conditions are relatively stable in their 

 instability, and so is the animal life to be found there. 10 



Muddy deposits. — The large amounts of organic materials con- 

 stantly brought into the sea by the rivers, and in the main also the 

 detritus from the rich littoral vegetation, are only slightly heavier than 

 sea water and sink very slowly to the bottom, being stirred up by any 



