ON GASTEROPODA. 361 
duals, they break them up with their shell, because it would’ 
be too difficult to separate them from it. But,” adds Aris- 
totle, “ care is taken to do all this when they are living, 
without which, if they died naturally, they would shed their 
fluid in expiring.” 
Pliny considerably abridges what Aristotle says concerning 
the purpura, and even modifies it in a manner nearly unin- 
telligible, which proves that he did not comprehend the text 
of Aristotle. He adds, “that they generally live seven years, 
though they grow much more quickly than other shell-fish, 
and attain their full size in about a year. They can live fifty 
days without eating. They remain concealed for thirty days 
during the dog-star heats; and it is especially on the coasts 
of Tyre in Asia, of Meninx, and Gitulor in Africa, and of 
Laconia in Europe, that the finest purple is to be found.” 
But he gives many interesting details respecting the species 
of shell-fish from which different colouring matters are 
derived. 
“There are two genera of shells which produce the purple 
colours, and the conchylian colours, colours which differ only 
in shade. The smallest is a buccinum, so called because it 
somewhat resembles that from which the sound of the horn is 
produced. Its aperture is round, and its edge emarginate. 
It is only found attached to stones, and in the neighbourhood 
of rocks. ‘The other is named purpura ; it is in the form of a 
club, and composed of seven whorls, which indicate its years, 
as in buccinum. But it is bristled with sharp points like 
needles, which do not exist in the latter. It is, moreover, 
provided with a projecting beak, (70strwm) and on the sides 
with small tuberculous spines, into which the animal can 
introduce its tongue.” 
“‘ The purpure are also distinguished by the denomination 
of pelagian, among which many varieties are established 
according to the places which they inhabit and the sub- 
