270 THE INHABITANTS OF THE SEA. 
CHAP. XV. 
MOLLUSCS. 
The Molluses in general.—The Cephalopods.—Dibranchiates and Tetrabranchiates, 
—Arms and Tentacles.—Suckers.—Hooked Acetabula of the Onychoteuthis.— 
Mandibles.—Ink Bag.—Numbers of the Cephalopods—Their Habits—Their 
Enemies—Their Use to Man—Their Eggs.—Enormous size of several species. 
—The fabulous Kraken.—The Argonaut.—The Nautilii—The Cephalopods of 
the Primitive Ocean.—The Gasteropods —Their Subdivisions.— Gills of the 
Nudibranchiates.—The Pleurobranchus plumula.—The Sea-Hare.—The Chitons. 
—The Patelle—The Haliotis or Sea-Ear.—The Carinarie.— The Pectini- 
branchiates—Variety and Beauty of their Shells—Their Mode of Locomotion. 
—Foot of the Tornatella and Cyclostoma.—The Ianthine.—Sedentary Gastero 
pods.— The Magilus.— Proboscis of the Whelk.— Tongue of the Limpet.— 
Stomach of the Bulla, the Scyllea, and the Sea-Hare.—Organs of Sense in the 
Gasteropods—Their Caution—Their Enemies—Their Defences—Their Use to 
Man.—Shell-Cameos.—The Pteropods—Their Organisation and Mode of Life. 
—The Butterflies of the Ocean.—The Lamellibranchiate Acephala—Their 
Organisation.—Siphons.— The Pholades.— Foot of the Lamellibranchiates.— 
The Razor-Shells.—The Byssus of the Pinne.—Defences of the Bivalves— 
Their Enemies. The common Mussel. — Mussel Gardens.—The Oyster. — 
Oyster Parks.—Oyster Rearing in the Lago di Fusaro.—Formation of new 
Oyster Banks.— Pearl-fishing in Ceylon.— How are Pearls formed? — The 
Tridaena gigas-—The Teredo navalis.—The Brachiopods.—The Terebratule.— 
The Polyzoa.—The Sea-Mats.—The Eschare,— The Lepraliz.—bBird’s Head 
Processes.—The Tunicata.—The Sea-Squirts.—The Chelyosoma.—The Botrylli. 
—The Pyrosomes.—The Salpx.—Interesting Points in the Organisation of the 
Tunicata. 
SIMPLE or compound, free or sessile, peopling the high seas 
or lining the shores, the marine Molluscs, branching out into 
more than ten thousand species, extend their reign as far as the 
waves of ocean roll. Though distinguished from all other sea- 
animals by the common character of a soft unarticulated body, 
possessing a complicated digestive apparatus, and covered by a 
flexible skin or mantle, under or over which a calcareous shell 
is generally formed by secretion, yet their habits are as various 
as their forms. Some dart rapidly through the waters, others 
creep slowly along, or are firmly bound to the rock; in some 
