432 



THE OCEAN WORLD. 



it forms a sort of fascia, or small band. The colouring matter, as it 

 is extracted from the animal, is yellowish ; exposed to the light, it 

 becomes golden yellow, then green, taking finally a fine violet tint. 

 While these transformations are in progress a peculiarly pungent 

 odour is disengaged, which strongly reminds one of that of assafcetida. 

 That portion of the matter which has not passed into the violet tint is 

 soluble in water ; when it has taken that tint it becomes insoluble. 

 The appearance of the colour seems provoked rather by the influence 

 of the sun's rays than by the action of the air. The matter attains 

 its final colour, in short, in proportion to the power of the sun's 

 rays. 



It is a question how far the colour evolved under the solar rays 

 remains indelible. It is known that the contrary is the case with the 

 colouring matter of the cochineal insect, which changes very quickly 

 when exposed to the sun. It is probably the remarkable resistance 

 it opposes to the rays of the sun which recommended it to the ancients. 

 The patricians of Eome, and the rich citizens of Greece and Asia 

 Minor, loved to watch the magical reflections of the sun on the 

 glorious colour which ornamented their mantles. 



But to return to our 

 humble shells. Pur- 

 pura lapillus (Fig. 277) 

 is a thick shell, oval 

 acute, with conical spiral, 

 generally of a faded or 

 yellowish white, zoned 

 with brown, and more 

 or less spotted. 



Purpura patula (Fig. 

 278) is very common in 

 the Philippines, and is 

 one of the handsomest 

 species ; its geographical 

 distribution has been a subject of much coEtroversy. 



Purpura consul (Fig. 279) is one of the large shells, and of a 

 fine salmon colour, with brown bands and a corona of spines. 



The Buccinums resemble the Purpura in many respects. Their 

 shell is oval or conical, much notched in front. They inhabit every 



Fig. 27 7* Purpnra la- 

 pillus. 



Fig. 278. Purpura patula. 



