DENTALTUM. 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. 



