UNIVALVE MOLLUSCA. 457 
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 probable that it was the remarkable 
resistance which this purple opposed to the rays of the sun which re- 
commended it to the ancients. The patricians of Rome, and the rich 
citizens of Greece and Asia Minor, loved to watch the magical reflec- 
tions of the sun on the glorious colour which ornamented their mantles. 
Fig. 287.—Purpura consul. Fig. 288.—Buccinum Fig. 289.—Buccinum undatum 
senticosum (Linnzeus). (Linnzus). 
But to return to our humble shells. Purpura lapillus (Fig. 285) 
is a thick shell, oval, acute, with conical spire, generally of a faded or 
yellowish white, zoned with brown, and more or less spotted. 
Purpura patula (Fig. 286) is very common in the Philippines, 
and is one of the handsomest species ; its geographical distribution 
has been a subject of much inquiry. 
Purpura consul (Fig. 287) is one of the large shells of this genus, 
and of a fine salmon colour, with brown bands and a corona of 
spines. 
The genus Buccinum resembles that of Purpura in many respects. 
Its shell is oval or conical, much notched in front. The species 
inhabit every sea, especially those of Europe. The animal has a 
