PHYLUM MOLLUSCA 



299 



Figure 188. A, shipworms (Teredo) exposed in their burrows in a piece of wood that has 

 been spht open. Teredo is a bivalve, but the two shells which are used for boring enclose only 

 a very small part of the anterior end of the body. The shipworm feeds on wood particles and 

 minute organisms. B, damage done to a wharf pile section, driven March, 1944, and removed 

 August, 1945. Every year these mollusks do millions of dollars worth of damage to wooden 

 wharf pilings and to ships. (B courtesy of William F. Clapp Laboratories.) 



most favorably known as food, especially the 

 bivalves. Aborigines of our own shores used 

 oysters in great quantities long before the 

 white settlers came to America. Proof of 



Figure 189. A pearl in a fresh- water clam; arrow 

 points to pearl. A fresh- water pearl has sold for as 

 much as $10,000. Pearls are protective secretions, 

 made of the same substance (nacre) that lines the 

 bivalve shell. (Courtesy of F.L. Clark.) 



the popularity of the oyster with the Indian 

 is found in the many piles of shells, that 

 have been found around onetime camping 

 grounds. Some of these piles contain tens of 

 thousands of bushels of shells, which in 



recent years have been mined for use in 

 road building and for manufacture of lime. 

 Oysters exceed in value any other kind of 

 marine animals used as food by man. About 

 30 million bushels are gathered annually in 

 the United States. Oyster culture is being 

 carried on with success. The soft-shell or 

 long-neck clam, Mya arenaria, and the hard- 

 shell clam, Mercenaria mercenaria, are 

 both widely used marine bivalves. The 

 edible clam is used for the famous Cape 

 Cod chowder. The edible mussel Mytilus 

 edulis (see colored frontispiece at beginning 

 of text) is eaten extensively in Europe but 

 not very much in this country. Only the 

 large adductor muscles of scallops (Pecten, 

 Fig. 170) are eaten. In certain parts of 

 Europe snails are considered a delicacy; and 

 one type of gastropod, the abalone, is a 

 common article of food on our western 

 coast. Squids (Fig. 183), cuttlefishes, and 

 octopuses are esteemed by palates in the 

 south of Europe and in the Orient. In the 

 United States, it is only because of prejudice 

 that people make less use of these clean 

 animals for food than do people of other 

 countries. But squids are used by the ton 

 for fish bait in America. 



