GASTROPODA. 



25 



most beautiful and strange forms. They are uuprovided with shells 

 except in the earliest stages of their existence, when they dwell in a 

 minute nautiloid shell, furnished with an operculum, both of which 



Fio;. 19. 



^3 



The Umbrella-shell (Umbraculum mediterraneuni). 

 a, shell ; b, gills ; c, tentacles ; d, mouth ; e, Toot. 



are subsequently cast off. Unfortunately the colours of these beauti- 

 ful creatures cannot be preserved after death, and therefore a small 

 series of glass models is exhibited, which will give some idea of 



\ 



Naked-gilled Mollusc, or Nudibranch (^Doto coronata). 

 a, liead ; b, foot ; c, gills ; d, tentacle-sheath ; e, tentacle. 



their great variety in form and colouring. They are found in most 

 parts of the world, chiefly in shallow water, but a few species live 

 ,upon floating seaweed in the open sea. Over a hundred species 

 exist on the British coast, the majority of which are, however, very 

 small. They are chiefly carnivorous, feeding on other molluscs, 

 sea-anemones, &c. 



Order 2. — Pulmonata. 



The Pulmonata are furnished with a lung-cavity in place of the Cases 

 ordinary gill of other Gastropods, and may be termed true air- 97-135. 



