THE BIVALVE MOLLUSKS. 703 



arctic seas and swarm near the surface at niglit, so that he need only drop his jaw and engulf 

 them by the hundred in his capacious mouth as he swims along with his head half out of water. 

 Probably the same thing is true of the other balsenoids. 



208. THE TUSK-SHELIS— SOLENOCONCHA. 



The class denominated in Professor Verrill's Check List Solenoconcha includes only one 

 moUusk that may concern us at present — Dentalium. This moUusk (chiefly D. pretiosum) occurs 

 all along the northern Pacific coast of America, and is known to Americans as the " Tusk-shell," 

 to Eussians as "Sookli," and to the Alaskan Indians as "Hya-qua." Prom Northern California 

 all the way to the arctic regions the coast tribes collected this shell, polished it, and arranged it 

 on strings as money — a circulating medium of trade, similar to the wampum of the eastern coast. 

 There were certain rules as to fineness, arrangement, size, and measurement, which decided the 

 value of the shells before and after stringing ; and so useful was this allococMcTc, as the California 

 Indians called it, that the Hudson's Bay Company and other traders adopted it as current coin 

 in their buying and selling of peltries and provisions. 



The strings of Bentalia were also worn as necklaces by the women, or twined in the hair of 

 both sexes; as trimming for garments, and ornaments for horse-trappings and the equipments of 

 war and the chase. Among other methods of employing them to enhance personal charm was to 

 insert two of them, point to point, from opposite sides, through a perforation in the partition 

 which separates the nostrils, which decoration was further increased by sticking a bright feather 

 in the large end of each of the hollow shells. This money is going out of use now, and only the 

 old Indians, conservators of ancient customs, attempt to hoard it up. A full account of it may be 

 found in the article upon ''Wampum" alreadj' alluded to, printed in "The American Naturalist" 

 for May, 1883. 



209. THE BIVALVES— lAMELLIBRANCHIATA. 



It is in the class of plate-gilled or lamellibranchiate moUusks, more popularly known as 

 "bivalves," that we find the most examples of direct utilization by man, or immediate contribu- 

 tion to the fisheries. Bivalves are widespread and well-known. They afford luxuries as well as 

 solid nourishment for our tables, enter largely into manufactured products, serve as ornaments, 

 and are so beloved by food-fishes generally that they are useful as bait. 



The partial list of bivalved mollusks that are ascertained to enter into the diet of Ameri- 

 can food-fishes includes the following, mainly from the northern Atlantic coast as in the case of 

 the gasteropods, and is instructive as showing how extensively fishes depend upon moUuscan 

 food: 



JEnsatella americana, Crytoda/ria siliqua, Mya arenaria, Spisula ovalis, Macoma sabulosa, Angulus 

 tener, Petricola pholadiformis, Venus mercenaria, Gyprina islandica, Cardium pinnulatvm, Oardium 

 islandicum, Gryptodon Oouldii, Venerieardia borealis, Astarte quadrans, Nucula proxima, Nucula 

 teMnis, Yoldia Umatula, Yoldia sapotilla, Toldia myalis, Toldia thraciformis, Leda tenuisulcata, 

 Argina pexata, Mytilus edulis, Modiola modiolus, Modiolaria discors, Grenella glandula, Pecten 

 tenuicostatus, Pecten islandicus, Pecten irradians, and Ostrea virginica; to which must be added 

 Unio, Anodonta, and other fresh-water bivalves, and the brachiopods Bhynconella psittacus and 

 TerebratuUna septentrionalis. 



In this lijt many species are of importance otherwise, and some worth notice, although not 

 fed upon by fishes, are not mentioned ; the first to be named in this latter class is the dreaded 

 Ship-worm [Teredo), of which there are seven species in the United States : 



