IV CONTENTS. 



Page. 



4. Mixed Systems. Lamark, 42 



5. Value of the characters employed. Valves of the shell. 



Canaliculated, dextral, operculated, pillared, multilocular, 

 free, gaping, equivalve shells. Muscular impressions. 

 Marginal impression. Ligament. Teeth. Borers, 9 



6. Review of the Linnsean genera, 75 



CHAPTER III. 



SYSTEMATICAL DISTRIBUTION or THE MOLLUSCA. 



I. Mollusca Cephala. 



1. Natantia. Cephalopoda. Cuttle Fish. Nautilacea. Se- 



piacea. Pteropoda. Limadna. Clio, J19 



2. Gasteropoda. Pulmonifera. Terrestrial. Aquatic. 



Branchifera. Branchiae external. Branclda internal, 1 44 



II. Mollusca Acephala. 



1. Conchifera. Brachiopoda. Lingula. Terebratula. Bi- 



valvia. Pectenidae. Ostreadce. Mytilida, 186 



2. Tunicata. Dichitonida- Ascidia. Pyrosoma. Mo- 



nochitonida. Salpa, 198 



CHAPTER IV. 



MOLLUSCOUS ANIMALS AS OBJECTS OF UTILITY. 



1. Employed as Food. Oyster. Mussel. Cockle. Pearl. Dye, 217 



2. Objects of Beauty. Preparation of Shells. Arrangement 



in a Cabinet, 229 



3. Mode of collecting Shells, 233 



4. Fossil Shells. Their systematical, chemical, geognostic, and 



geographical history, 235 



