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LOWER COASTAL ANIMALS 



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Tropical mud-Jiats are populated by a host of molluscs. India. 



At the lowermost extent of the tidal zone are animals which cannot 

 tolerate desiccation; the creatures we find here, in other words, are those 

 which dwell in the next, shallow-water zone. But if the degree of desic- 

 cation determines the vertical distribution, it is the bed which conditions 

 the horizontal. Rocks are admirably adapted for adhesion by clinging, 

 suction, or cementing, but not so shifting sand or soft mud and clay. On 

 all loose floors it is the burrowing animals which predominate, and they 

 vary according to whether the bed is of gravel, sand, clay, or ooze. 



The sandy shores all down the west coast of Africa presented a desolate 

 appearance; but on closer inspection we found that they were not nearly 

 so desolate as they had seemed. The fact is that they are badly adapted 

 for animals to move about on by day. Only a few ghost crabs (Ocypode) 

 are visible, running up and down with the breakers and looking like 

 flecks of foam tossed hither and thither. Everywhere — not only in 

 Africa but on all tropical sandy shores — are quantities of crab holes, 

 many of them the size of rat holes, and these may be found close to the 

 nearest coastal plants, on St. Thomas even among the coconut palms. The 

 ghost crabs are typical roving animals, feeding on prey or carrion. Many 

 smaller forms, such as Scopimera and Dotilla, live more peacefully on the 



