140 THE HALL OP SHELLS. 



some were fine as silk, in otliers stiff and 

 homy. These were attached by strong mus- 

 cles to themselves, and thence to rock, reef, 

 or wreck, as pleased the little spinner. 



" These threads are spun by the foot of the 

 little animal, and are so stout as to withstand 

 the shock of the incoming seas. When wish- 

 ing temporary anchorage, or fearing the stress 

 of waves, it has only to throw out its byssus 

 cable and rest secure. Sometimes this little 

 bark with its silken moorings is freighted with 

 pearlsj" said he, pointing to a mussel; "the 

 pearls of these shells, however, are generally 

 of an inferior order. 



"The Pinna, or fan mussel, is a byssus 

 spinner, having valves two feet long ; and the 

 beautiful silk of its byssus has been used in 

 spinning rich and costly fabrics. 



" We find among these not only the spin- 

 ners of silk, but borers of wood and stone, and 

 hence some of them have received the name 

 ' wood eaters ' or ' stone eaters.' 



" How these little creatures are able to bore 

 into hard substances has long been a question 

 of wonder and speculation. The serrated or 

 filelike edges of some shells might seem to 

 account for it in a measure ; the abrading foot 

 with its strong muscles, sometimes assisted by 



