MOLLUSCA. 227 



testaceous matter ; in the latter, the matter seems to be ac- 

 cumulated against the internal opening of some hole with 

 which the shell has been pierced by some of its foes. Lin- 

 naeus, from the consideration of this circumstance, endea- 

 voured, by piercing the shell, to excite the animal to se- 

 crete pearl ; but his attempts, though they procured him a 

 place among the Swedish nobility and a pecuniary reward, 

 were finally abandoned ; the process being found too tedi- 

 ous and uncertain to be of any public utility. The largest 

 pearl of which we have any notice, is'one which came from 

 Panama, and was presented to Philip II. king of Spain, in 

 1579- It was of the size of a pigeon's egg. Sir Robert 

 Sibbald mentions his having seen pearls from the rivers of 

 Scotland as large as a bean. 



Besides yielding us a variety of wholesome food, and valu- 

 able ornaments, testaceous animals supply us with a beauti- 

 ful dye. The Purpura of the ancients, according to the 

 opinion of Rondeletius, confirmed by the' observations of 

 Cuvier, was chiefly extracted from the shell termed Murex 

 brandaris. Since the introduction of the cochineal insect, 

 the use of this dye has been superseded, so that we are now 

 in a great measure ignorant of the process which the an- 

 cients employed to extract it. In Britain there are several 

 kinds of shell-fish, which furnish a dye of this sort, but these 

 are seldom sought after. Cole, in 1685, published a method 

 of obtaining it from the Purpura lapillus, to which Mon- 

 tagu, in the supplement to Testacea Brittanica, has added 

 several important directions. When the shell is broken in 

 a vice, there is seen on the back of the animal, under the 

 skin, a slender longitudinal whitish vein, containing a yel- 

 lowish liquor. When this juice is applied to linen, by means 

 of a small brush, and exposed to the sun, it becomes green, 



