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PACIFIC SCIENCE, Vol. XX, April 1966 
Fig. 4. Hummocks made prior to the emergence of the crabs. (The ruler is 15 inches long.) 
Fig. 5. Holes opened by emergence of the crabs. (The ruler is 15 inches long.) 
crabs may feed for periods of the order of 2 hr, 
it would seem impossible for the gut to accom- 
modate a continuous intake of sand for this 
length of time. The fact that they habitually 
feed for such extended periods favours the ex- 
planation that they need to sample a large 
volume of sand, and that they efficiently select 
from this the small fraction suitable for inges- 
