SHELL-CAMEOS. 2!»7 



defence, we may naturally expect a considerable degree of 

 caution, and in this respect the gasteropoda might give many 

 useful ressons to man. How carefully they protrude their ten- 

 tacles as far as possible to sound every obstacle in their way, 

 before they creep onwards, and how rapidly they withdraw 

 into their shell at the least symptom of danger ! What an 

 example to so many of us that leap before they look, and fre- 

 quently break their necks in the fall ! 



Yet, in spite of all their prudence and of the protection of 

 their stony dwellings, they serve as food to a host of powerful 

 enemies. The sea-stars, their most dangerous foes, not only 

 swallow the young fry but also seize with their long rays the 

 full-grown gasteropods, and clasp them in a murderous embrace. 

 They are preyed upon by fishes, crustaceans, and sea-birds, 

 who pick them up along the shores; but it will sometimes 

 happen that a crow, while endeavouring to detach a limpet for 

 its food, is caught by the tip of its bill, and held there until 

 drowned by the advancing tide. J 



Man also consumes a vast number of sea-snails, for on every 

 coast there are some edible species ; and it may be said that, with 

 the exception of very few that have a disagreeable taste, they 

 are all of them used as food by the savage. The miserable 

 inhabitants of Tierra del Fuego chiefly live upon a large limpet 

 that abounds on the rocky shores of their inhospitable land, and 

 but for this resource would most likely long since have been 

 extirpated by hunger. 



Many of the univalve shells are, moreover, highly prized as 

 objects of ornament or use both by savage and civilised nations. 

 The South Sea Islander makes use of a Triton as a war conch ; 

 the Patagonian drinks out of the Magellanic volute, the Arab 

 of the Eed Sea employs a large Buccinum as a water-jug, and 

 the Cyprcea Tnoneta is well-known in commerce as the current 

 coin of the natives of many parts of Africa. In Europe the iri- 

 descent Haliotis is frequently used for the inlaying of tables or 

 boxes, and various species of Helmet-shells and Strombi (Cassis 

 rufa madagascwriensis, Strornbus gigas), peculiar as being 

 formed of several differently coloured layers, placed side by side, 

 are in great request for the cutting of cameos, as they are soft 

 enough to be worked with ease, and hard enough to resist wear. 

 More than two hundred thousand of these shells are annually 



