INDEX. 



581 



CHAPTEPt XVII. 



Fourth Class of Mollusca : — 

 Brachiopoda, their arms 

 Contrivance for procuring food 



CHAPTER XVIII 



Fifth Class of Mollusca :— 



Gasteropoda .... 

 Why so called .... 

 Different orders of, how distinguished 

 Air-breathing gasteropods . 

 Terrestrial, how recognisable 



Slugs 



Snails ..... 



Aquatic air-breathing gasteropods. 



Their operculum, or door 



Their eyes on footstalks 



Cm-ious egg-cases ... 



Wentle-trap .... 



Legend of the origin of the Tyrian dye 



Its changes of colour . 



Stromb-shells .... 



T ubulibranchiata 



Their tube-shell and door . 



Scutibranchiata, sea-ears 



Keyhole limpets 



271 



272 



273 

 273 

 273 



275 

 275 

 275 

 276 

 276 

 277 

 278 

 278 

 278 

 282 

 283 

 284 

 284 

 285 

 285 

 286 



2 c 2 



