62 MOLLUSCA. 
they have no operculum. They are found in many seas, 
196 living and 150 fossil species being known. 
VALUE.—In Califoraia they are eaten. In 1880, 6,372 sacks of Al- 
balones, or Haliotis, valued at $46,179, were shipped from that State, 
and probably as many more by rail. They find a market in New York 
and Boston, where they are either cut or powdered and made into but- 
tons, etc. 
Violet Snails (Zanthinide).—These shells (Fig. 65, I) 
float upon the surface of Southern waters, and are tinted 
with purple and violet, the animal when pressed emitting 
Fic. 65.—I, /anthina, the ocean-snail : S, foot ; 7, raft of air-bubbles, with 
egg-bags hanging down. C, Carinaria: f, foot; 5, Shell covering the 
breathing-gills, g. Both these forms float upside down. P, Preropod. 
a rich purple indelible ink. They secrete by their foot 
a curious raft, composed seemingly of bubbles of air in 
transparent sacs. This buoys them up, and is also a nur- 
sery, the eggs being attached to the under portion, the 
entire family being at the mercy of the wind. 
