[57] FISHERIES OF THE UNITED STATES. 241 



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in San Francisco markets to that of the small-sized Venus mercenaries, 

 used so extensively in the Eastern States. 



Tapes laciniata, Cpr., is a closely allied species, and has about the 

 same distribution as T. staminea. No distinction is made in the markets 

 between them, both being sold as "Little-Neck" or " Hard-Shell" clams. 

 They are the most abundaut and extensively used of all the clams in- 

 digenous to the coast; but of late, since the introduction of the Mya 

 arenaria, they have been supplanted in the markets to a great extent 

 extent by that animal. 



Ghione succineta, Val., and Chione simillima, Sby., are also known in 

 the markets as "Little-Neck" clams, but are not so abundant as Tapes. 

 They live on sandy beaches on the California coast, and especially in 

 Monterey Bay and other sheltered localities, but are not found in suffi- 

 cient numbers to be of much importance as a food supply. 



Saxidomus arattis, Gould. 



This is the " Eound Clam " of the Pacific coast. It is found from San 

 Francisco to the southward to San Diego, but is not abundant. Mon- 

 terey and San Diego produce it in largest numbers. It is probably only 

 a southern variety of the northern shells of this genus. 



Teredo. 



There are four species of the genus Teredo found on the coast of the 

 United States, and also an allied species, the Xylotrya Jimbriata, of Jeff- 

 reys, having similar habits. The Teredo navalis, Linne, is the most 

 abundant, and extends from Vineyard Sound to Florida. The Teredo 

 megotara, Hanley, is found from Massachusetts Bay to South Carolina. 

 The Teredo Thomsonii, Tryon, is indigenous, but its distribution has not 

 yet been thoroughly determined ; the Teredo dilatata, Stimpson, occurs 

 from Massachusetts to Florida, and the X. jimbriata has the same range. 

 These creatures are usually known as ship- worms and inhabit submerged 

 wood-work, floating or stationary, and frequently do great damage. 

 An instance is recorded of the piles of a wharf at Cape Henry having 

 been destroyed in nine days by their ravages. Though they burrow 

 into all submerged wood- work, it is for protection and not for food, and 

 the excavations once made are neatly lined by the animal with shelly 

 material. While at the surface the holes are very small, having been 

 made by the young Teredos; as they go deeper, they gradually grow 

 larger, and are sometimes 10 inches in length and one-quarter inch in 

 diameter. The tubes, however they may enter the wood, usually turn, 

 at a short distance from the surface, in a direction parallel with the 

 grain. The burrow of one animal never interferes with, or crosses that 

 of another, and a thin partition of wood is always left between the tubes. 

 The tendency to follow the grain is not due to necessity, for tlie Teredo 

 can bore through the hardest knots; nor is it necessary that the tubes 

 should be straight, for they are often very crooked and tortuous, 

 2444— Bull. 27— 1G 



