XV THE HALL OF SHELLS. 
mollusks tenanting these shells surpass the marvelously 
contrived houses-in which they live. The power of adhe- 
sion possessed by the Patella and its ability to sustain 
great weights should be tested by those who have access 
to seacoasts. Read Mollusca, their Shells, Tongues, Eyes, 
and Kars, by Philip Henry Gosse, F. R.S. Examine com- 
mon garden snails, comparing their eyes with those of the 
Pecten upon the seacoast. 
CHAPTER III.—The extensive use of Purpuras and 
Murexes in the ancient dying of purples is shown by the 
little mountains of shells still lying in vicinities where 
this industry was plied. The coloring matter—but a drop 
—contained in a veinlike sac. The Purpura the crest of 
the city of Tyre. Study Tyre, and learn of the caldron- 
like cavities in the rocks where these shells were crushed. 
Compare the shells of this family, noting how the whorls 
of some of these shells are thickened by varices or nodes, 
indicating rest periods in growth; also the immense de- 
velopment of the last whirl in some; the elongated spines 
in others. 
CHAPTER IV.—Observe with a strong microscope the 
beauty of coil and polish in the most minute shells. 
Where living specimens can be examined the tenants of 
these diminutive shells will be found to possess as compli- 
cated and delicate organisms as those of larger growth. 
Study sand from any sea beach. Shake the sand and 
atoms from sponges on sale, then count and examine the 
treasures you will find. 
CHAPTER V.—Undine finds a “sea horn” among her 
shells. It is the shell Neptune’s trumpeter is fabled to 
have used to still the tumult of the sea. Tritonia tritonis 
used as a teakettle, the operculum its cover. Ianthina fra- 
. gilis, preserved through the beating of waves and the 
grinding of sand, bears its egg capsules beneath a float, 
and buoyed up upon the tossing seas the delicate creatures 
are born to the purple. 
The horny operculum of land snails may be seen, and 
