CONTENTS. XI 



XI. 



HALF AN HOUR WITH SHELL-FISH (UNIVALVES). 



Beauty and popularity of shells. Mathematical laws of con- 

 struction. Moseley on ditto. Divisions of the group. The 

 Cephalopoda, or " Cuttle-fish." Geological antiquity of 

 many groups. The " Octopus." Physiological details of 

 the structure of "Cuttle-fish." Calamaries and squids. 

 Sepia. " Sea-grapes," the eggs of Cuttle-fish. Loligo. 

 The Pteropoda. The Gasteropoda division of mollusca. 

 Naked-gilled ditto. Univalves. Limpet, Chitons, Trochus, 

 Littorina, Nassa, Cyprea, Purpura, Natica, Dentalium. 

 Whelks, &c. Egg-cases of latter, &c. . . Pages 179 to 204 



* 

 XII. 



HALF AN HOUR WITH SHELL-FISH (BIVALVES). 



Fertility of mollusca. Geological importance of their valves. 

 The JBrachiopoda. Their geological antiquity. Relation 

 to sea-mats. Their physiological structure. The Lamelli- 

 Iranchiata. General structure. Mussels, '* Razor-shells," 

 Scallops, &c. Mr. Gosse's 'description of latter. Pholas : 

 its boring powers. Speculation on ditto. How achieved. 

 The Mactras, Tellinas, Donax, &c. Mya arenaria and 

 truncata. Thracia, Tapes, '' Otter-shells," &c. Astartes, 

 Lucina, Cyprina, Crenella, Nucula, Leda, Pectunculus, 

 Pinna, &c. The smaller species .... Pages 205 to 227 



XIII. 



HALF AN HOUR WITH CRUSTACEA. 



Changes in the young of Crustacea. Relation of barnacles to 

 crabs and lobsters. Balanus, Scalpellum, Lepas, &c. 

 Transformations of former. The physiological structure of 

 the Cirripedia. Division of Crustacea into groups de- 

 scribed. Physiological characters detailed. The " Spider- 

 Crabs. " The great, or common crab. Moulting of Cms- 



