Mother-of-Pearl Shell. 85 



island in the Sooloo Archipelago, without change, 

 close to the golden-edged shell. The golden-edged 

 is less infected with "worms' or "borers," such 

 as the LitJwdomiis, (see Fig. i) a small bivaKe 

 that eats into the shell, piercing; it dccpl}'. 



FiQ. 1. LITHODOMUS. 



(Natural size). 



The horny lip of the shell is deep, and in 

 some places the two valves are very similar in 

 appearance. 



On the Australian coast both golden and 

 black-edged shells are found, but they are some- 

 what coarser and more worm-eaten, although as 

 bright and lustrous as the best Sooloo shell. In 

 all varieties, the horny lip is sufficiently flexible to 

 make a tight joint when the shell is closed. 



The sea bottom most favourable for shells is 

 subject to wide variation. A reefy bottom near to 

 mud is however generally considered as good 

 holding ground as any, especially when there is a 

 luxuriant growth of weeds, and more particularly 

 coral cups, and a beautiful growth on the coral 

 resembling coach whips, four or five feet in length. 



The common Mother-of- Pearl shell consists of 



