Belding. — Conditions Regulating Clam Growth 127 



of soil provided that it is not shifting sand or soft mud. 

 Even in such cases exceptions are frequently noticed, 

 clams often being present where there is moderate shift- 

 ing, while large clams are occasionally found in 

 extremely soft mud. To insure the best growth, the soil 

 should be free from decaying organic matter, it should 

 be of firm consistency, not readily affected by storms 

 or currents and free from substances which might injure 

 the clam. Any soil possessing these qualifications, no 

 matter its exact composition, is suitable for clam growth. 



Soils may be grouped into three main classes, sand, 

 mud and gravel, with many intervening combinations. 

 Flats of fine sand, usually swept by a current, furnish 

 the best appearing clams with a smooth white shell in 

 marked contrast to the rough and deformed gravel clam. 

 Mud flats are usually situated where there is little cur- 

 rent or where streams deposit material from the land 

 and in most instances produce a slower growing clam. 

 Gravel flats, though less extensive, nearly always contain 

 clams which by reason of their environment have a 

 heavy protecting shell. 



Unproductive Soils. — Tidal clam flats are of two classes, 

 productive and unproductive. Usually the boundary line 

 is sharply marked, but at times no noticeable difference 

 can be seen except that one flat produces clams while the 

 other does not. The unproductive flats can be further 

 grouped into permanent and temporary, the latter includ- 

 ing the flats where clams will grow if planted, but which 

 either do not receive the set, or owing to changed natu- 

 ral conditions are temporarily unproductive. This type 

 of flat is especially adapted for clam culture. The per- 

 manent barren flats comprise soils that can never be re- 

 claimed, soils that can only be utilized after considerable 

 expense, and soils that can be made productive at a slight 

 cost. 



There are several classes of unproductive soils. (1) 

 Soft mud smothers the small clams, prevents the set by 

 reason of its slimy surface and, by the fine particles 

 of silt, interferes with the mechanical feeding of the 



