318 
THE M A GIL US . 
fissure is caught against the sharp front edge of the shell, and thus undergoes involuntary 
amputation. 
The general colors are tolerably similar throughout the Harps, but each species always 
preserves its peculiar individuality. One species, for example, has the spaces between the 
ridges pencilled in elaborate wavy markings of chocolate on white, and the ribs themselves 
barred at regular intervals by lines of deep brown ; while another, known by the name of 
A extricose Harp (Ilarpa ventricdsa), has the spaces filled with a succession of arches, one 
within the other, and of a rich brown color. 
A very common shell may often be found on the seashore, looking like a small whelk with 
a smooth whitish shell, boldly banded with reddish-brown. This is the Co mm ox Purple, or 
Purpura ( Purpura lapillus ), another member of this genus, and worthy of notice as being one 
of the shells which furnish the celebrated Tyrian purple of the ancients. This color, which, 
by the way, contains so little blue as to be unlike the tint which we now call by the name of 
purple, is evidently the analogue of the ink found in the sepia, and is secreted in a little sac 
by the throat, containing only one small drop. 
For the very best dye this material was extracted carefully from the individual shells, but 
for an inferior kind it was obtained by pounding a quantity of the Purpurse in a mortar, and 
straining olf the juice, which was thus mixed with the blood and general moisture of the 
animals, and consequently of less value than the pure dye. So expensive was the dye obtained 
by this latter process, that a pound of wool stained with it could not be purchased under 
a sum equalling one hundred and fifty dollars. Any one can try the experiment of dyeing 
a little strip of linen with the matter obtained from a single shell. After breaking the shell 
carefully so as not to crush the inhabitant, the cell containing the coloring matter will be seen 
lyi n §> across the head or neck of the animal, and can be removed by opening the sac and 
taking up the yellowish-white contents with a small camel’ s-hair brush, or the point of a new 
quill-pen. When the linen is imbued with this liquid and placed in the rays of the sun, it 
immediately begins to change its color, and passes through a series of tints with such rapidity 
that the eye can hardly follow them, unless the slanting rays of the rising or setting sun are 
chosen for the purpose. 
Oxe of the strangest, though not the most beautiful, of shells is the Magilus, a native of 
the Red Sea and the Mauritius. 
During its stages of development, the Magilus appears once as a small and delicate shell 
and then as a long, crumpled, and partly spiral tube, with a shell at one end and an opening 
at the other. 
For the purpose, apparently, of carrying out some mysterious object, the Magilus resides 
wholly in the masses of madrepore, and in its early youth is a thin and delicate shell without 
anything remarkable about it. As it advances in age, it enlarges in size, as is the case with 
most creatures ; but its growth is confined to one direction, and, instead of enlarging in diam- 
eter, it merely increases in length. The cause of the continual addition made to its length is 
probably to be found in the growth of the madrepore in which it is sheltered, and which would 
soon inclose the Magilus within its stony walls did not the mollusk provide against such a fate 
by lengthening its shell and taking up its residence in the mouth. 
The most curious point, however, in the economy of the Magilus is, that, as fast as it adds 
a new shell in front, it fills up the cavity behind with a solid concretion of shelly matter, very 
hard, and of an almost crystalline structure, so as to leave about the same amount of space as 
in the original shell. The animal is always to be found in the very front of the shelly tube, 
and closes the aperture with a strong operculum that effectually shields it against all foes. 
The color of the Magilus is whitish. Only one species is known. 
In the peculiar formation of the shell there is an evident analogy with the successive 
chambers formed by the pearly nautilus. In both cases the animal is of small dimensions 
when compared with the magnitude of its dwelling, and in both cases the creature continually 
advances forward, taking up its residence in a chamber formed in the front of the shell, and, 
closing the passage behind in proportion to its advance. The chief difference, how T ever, 
