CHAMACEA. 309 



Large pearls are occasionally found in the Trklacna gigas. 

 One, exhibited at Sir Joseph Banks^s, in June 1804, was 

 valued at two or three hundred pounds. The colour of 

 this extraordinary shell is of a dirty white, or yellowish or 

 reddish brown. The hinge is furnished with a cartilage of 

 a dull brown colour, but, when cut and polished, is beauti- 

 fully iridescent as the opal. 



The genus Hipjoopus presents a curiously imbricated shell, 

 of which the interior is lined with clear white enamel, trans- 

 parent as alabaster. The muscular impression is not spread 

 out towards the central margin, as in the previous genus : 

 these, although not very important differences, are peculiar 

 and unchangeable, 



I'amily VI. Chamacea. 



Who lias not heard of tiny folks that dance 



in green and gold, when shine the bright moonbeams, 



Or sportive elves, that take all curious shapes 



Of fantasie ? But far less beauteous they. 



Less wonderful, than those that calmly dwell 



Beneath the waters. 



Next in the descending scale is the Order Bimuscnlosa, 

 which includes such mollusca as are attached to their shells 

 by two adductor muscles, the marks of which attachment 



