62 



MOLLUSC A. 



they have no operculum. They are found in many seas, 

 196 living and 150 fossil species being known. 



VALUE. In California 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 (lanthinida!). These shells (Fig. 65, I) 

 float upon the surface of Southern waters, and are tinted 

 with purple and violet, the animal when pressed emitting 



FIG. 65. I, lanthina^ the ocean-snail : /, foot ; r, raft of air-bubbles, with 

 egg-bags hanging down. C, Carinaria : f, foot ; s, shell covering the 

 breathing-gills, g. Both these forms float upside down. P, Pteropod. 



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. 



