Handbook of Paleontology 109 



upon other mollusks, as the Urosalpinx or Oyster Drill 

 that is so destructive to oyster beds ; there are also 

 boring sponges. Starfishes prey upon bivalves and 

 are very detrimental to mussel beds. In no other area 

 are the weapons of offense and defense and the tactics 

 of warfare so varied as they are at the shore. Apart 

 from the distinct organs of offense and defense, there 

 are distinct habits or tactics which are the outcome 

 of the shore struggle. Among the tactics to escape 

 pursuers are hiding, masking, protective coloration or 

 resemblance, warning coloration, mimicry, death- 

 feigning, rapid flight etc. Sometimes these tactics are 

 aggressive in character, helping an animal stalk its 

 prey. Hiding is one of the commonest means of escap- 

 ing pursuers. The animals using this method hide 

 under stones or seaweed, burrow, or, as the Hermit 

 Crab, take refuge in empty gastropod shells. Crabs 

 (Carcinus, Cancer) and other crustaceans make use of 

 death-feigning or hypnosis. There is a sudden cessation 

 of activity and the animals give the appearance of death. 

 In protective resemblance there is a close resemblance to 

 the surroundings. Crabs are found resembling pebbles, 

 branches of coral, mollusk shells, muddy surface of lime- 

 stone etc. ; nudibranchs are found on green or red sea- 

 weeds according to their color; the polychaete worm, 

 Eulalia viridis, is found on green seaweed, Ulva, which 

 blends with its own green color. Many examples of this 

 kind might be given. In contrast to this, some colora- 

 tion is very conspicuous and is associated with unpalata- 

 bility or qualities which make the animal dangerous to 

 eat. It therefore acts as warning coloration. There have 

 been recorded only a few cases of mimicry at the shore, 

 that is, resemblance of some harmless form to one that 



