Fig. I Drawn from living clam .4mm (less than one fiftieth of an inch) in length. S, siphons, 

 two tubes, one of which conducts water bearing food and oxygen to the body within the shell, 

 the other conducting a stream containing waste matter to the exterior. F, foot, the organ of 

 locomotion. B, byssus, a delicate thread for attachment, which is not present in the adult. 



