BENTALIUM. 
109 
connecting muscle, as in other genera, is attached. 
It is true, that both in this and the following genus, 
the animal does not appear to be restrained in his 
motions within the limits of his house ; but it by 
no means follows that he has not some tie to 
prevent his leaving it. Were he perfectly at 
liberty, the form of his receptacle would scarcely 
preclude the action of the water or accidental vio- 
lence from forcing him from it against his will. 
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