NON -PULMON ARY GASTEROPODS. 
409 
The genus Bulla differs materially from the Aplysdffi. They hare 
a Well-developed shell, the form of which is elegant ; they are delicate 
111 structure ; their brilliant colours, consisting of red, black, or white 
^auds, separated by many varied tints, cause these little molluscs to 
■ )<! much sought after for ornamental collections. The shell itself is 
°val or globulous, rolled up in a scroll, smooth, spotted, very thin and 
fragile, with a concave spiral, umbilicate, open in all its length, with a 
straight, wide, and cutting edge. 
Figs. 206 and 207. Bulla ampulla (Liunauis). 
Obtuse at its two extremities, neither the head of the animal nor 
tentacles are very apparent. The gills are placed under the back, 
a little to the right and behind ; its stomach, which alone fills a great 
Fig. 208. Bulla oblonga 
(Adams). 
Fig. 209. Bulla aspersa 
(Adams). 
Fig. 210. Bulla nebulosa 
(Gould). 
P ai ’t of the cavity of the body, presents the peculiarity, already noted 
111 the Aplysia, of being furnished with bony pieces, evidently intended 
fr grind the food. 
The Bullae can swim with facility in deep water, but they evidently 
Prefer the shallows and a sandy bottom, feeding upon smaller mol- 
Usc s. They are found in every sea, but they abound chiefly in the 
