270 THE INHABITANTS OF THE SEA. 



CHAP. XV. 



MOLLUSCS. 



The Molluscs in general. — The Cephalopoda. — Dibranchiates and Tetirabranchiates. 

 — Arms and Tentacles. — Suckers. — Hooked Acetabula of the Onychoteuthis. — 

 Mandibles.— Ink Bag. — Numbers of the Cephalopoda — Their Habits— Their 

 Enemies — Their Use to Man — Their Egga. — Enormoua size of several species. 

 — The fabulous Kraken. — The Argonaut. — The Nautili. — The Cephalopods of 

 the Primitive Ocwin. — The Gasteropods — Their Subdivisions. — Gills of the 



Nudibranchiates The Pleurobranchua plumula. — The Sea-Hare. — The Chitons. 



— The Patellae. — The Haliotis or Sea-Ear. — The Carinariae. — The Pectini- 

 branchiates — Variety and Beauty of their Shells — Their Mode of Locomotion. 

 — Foot of the Tornatella and Cyclostoma. — The Ianthinae. — Sedentary Gastero 

 pods.— The Magilus.— Proboscis of the Whelk. — Tongue of the Limpet- 

 Stomach of the Bulla, the Scyllsea, 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 Pholadea. — Foot of the Lamellibrancbiates. — 

 The Eazor-ShelLs. — The Byssus of the Pinnae. — Defences of the Bivalves— 

 Their Enemies. — The common Mussel. — Mussel Gardens. — The Oyster. — 

 Oyster Parks — Oyster Bearing in the Lago di Fusaro. — Formation of new 

 Oyster Banks. — Pearl-fishing in Ceylon. — How are Pearls formed?— The 

 Tridacna gigas. — The Teredo navalis. — The Brachiopods. — The Terebratulse. — 

 The Polyzoa. — The Sea-Mats. — The Escharae. — The Lepraliae. — Bird's Head 

 Processes. — The Tunicata. — The Sea-Squirts. — The Chelyosoma. — The Botrylli. 

 — The Pyrosomes. — The Salpae. — Interesting Points in the Organisation of the 

 Tunicata. 



Simple or compound, free or sessile, peopling the high sea* 

 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 



