240, DIVISION II. MOLLUSCOUS ANIMALS.— CLASS IV. ACEPHALES. 
the heap of rottenness. The pearls are drilled and strung in Ceylon— _ | 
a work which is performed with admirable dexterity and quickness. For | 
cleaning, rounding, and polishing them, a powder of ground pearls is made 
use of. 
“The Pacifie also furnishes these costly ornaments to wealth and beauty ; 
but the pearls of California and Tahiti are less prized than those of the 
Indian Ocean. 
“ Pearl-like excrescences likewise form on the inner surface of our oysters 
and mussels, and originate in the same manner as the true pearls. The 
formation of the pearl, however, is not yet quite satisfactorily accounted 
for. Some naturalists believe that the animal accumulates the pearl-like 
substance to give the shell a greater thickness and solidity in the places 
where it has been perforated by some annellide or gasteropod. According 
to Mr. Philippi, an intestinal worm stimulates the exudation of the pearl- | 
like mass, which, on hardening, encloses and renders it harmless. 
“ Brillianey, size, and perfect regularity of form are the essential quali- 
ties of a beautiful pearl. Their union in a single specimen is rare, but it 
is of course still more difficult to find a number of pearls, of equal size and 
beauty, for a costly necklace or a princely tiara.” | 
Precren. — The Clam. This valuable mollusk, in its numerous varieties, | 
is too well known to need description. It ranks next to the oyster, and is | 
everywhere highly prized as an article of food. The shores and crecks of 
all seas supply inexhaustible quantities of clams, which not only furnish the 
inhabitants with a cheap and nutritious aliment, but are extensively used as 
bait for cod and other fishes. The fresh-water varieties are not edible. | 
Sronpy us. — Like the oyster, these animals have a rough, foliated shell, 
which, however, is often armed with spines, and is usually beautifully col- | 
ored, for which reason it is highly valued. The shells often sell at enormous 
prices, and ornament the cabinets of wealthy amateurs. “A Parisian pro- | | 
fessor once pawned all his silver spoons and forks to make up the sum of 
six thousand francs, which was asked for a royal Spondylus ; but on return- 
ing home, he was so warmly received by his lady, that, overwhelmed by the 
hurricane, he flung himself on a chair, when the terrific cracking of the 
box containing his treasure reminded him too late that he had conecaled 
it in his skirt pocket. Fortunately but two of the thorns had been broken 
off, and the damage was susceptible of being repaired; his despair, how- 
ever, was so great, that his wife had not the heart to continue her reproaches, 
and in her turn began to soothe the unfortunate collector.” 
Mytitus. — The Mussels. These mollusks have a cloak open in front, 
but with a separate excremental aperture. They have a foot with which they 
progress, and fix their byssus. Some of the species are smooth, others are 
