94 A NATURAL HISTORY OF THE SEAS 



and swallowing whole large pieces of eel grass, which 

 it grinds up in a powerful gizzard. The gills are protected 

 by a thin horny shell very like a human thumbnail, and 

 this is in turn covered by two flaps of skin. These may 

 be used as wings, the animal clumsily flapping its way 

 through the water. Though eaten by certain fishes, 

 the mollusc can discourage or escape from foes by exuding 

 great quantities of a vivid purple fluid, which, like the 

 ink clouds of the cuttlefish, may obscure the water for 

 several yards around. It further gives out a whiteish 

 fluid of a poisonous nature which was appreciated by the 

 ancient Greeks, who employed it to remove unpopular 

 personages. The animal can give out a powerful cedar 

 oil, which frequent washing scarcely succeeds in eradicating 

 from the hands once they have touched a Sea Hare. The 

 eggs are laid in long threadlike strings amongst weeds 

 and corallines. 



The Umbrella Snails (Umb?-acculum) are huge shapeless 

 creatures with a small shell shaped like a Chinese parasol. 



The Bubble Shells {Bulla, Acton and Scaphander) are 

 allied to the Sea Hares, but the animals are contained in 

 large globulous shells of beautiful form and colour. 

 Scaphander Ugnarius — the Boat Shell, of our southern 

 coasts — burrows in sand, where it devours bivalves, etc. 

 The food is ground up in a remarkable calcareous gizzard 

 composed of two plates like millstones about the size of 

 a threepenny bit. 



Very unlike any of the preceding yet nearly related 

 anatomically are the fairylike Sea Moths or Sea Butterflies, 

 which form dense clouds covering vast areas of the northern 

 seas. The discarded shells of dead specimens sink to 



