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MANUAL OF ZOOLOGY 



and the animal lies with the ventral valve uppermost and the two 

 valves gaping slightly. The end of the valve at which the peduncle 

 is situated is regarded as posterior, the opposite end as anterior. The 



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two valves articulate together by a more or less distinct hinge situated 

 at the posterior end, and the movements both of opening and of closing 

 the shell about this hinge are effected by means of muscles passing 

 internally between the valves. 



