. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. i)r)0 CAIJFORXIA FISH AND GA:ME Rings Tlie shells of many individuals are marked by eoneentrie rings of alternately darker and lighter eoloi-ation. At irregular intervals the gen- eral opacity of the shell is interrui)ted by translucent rings which can be seen on fresh shells (particnhii'ly dams less than five years of age) by holding the shell to a strong ligiit somewhat in the same manner as one would candle hens' eggs. Both minor a
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. i)r)0 CAIJFORXIA FISH AND GA:ME Rings Tlie shells of many individuals are marked by eoneentrie rings of alternately darker and lighter eoloi-ation. At irregular intervals the gen- eral opacity of the shell is interrui)ted by translucent rings which can be seen on fresh shells (particnhii'ly dams less than five years of age) by holding the shell to a strong ligiit somewhat in the same manner as one would candle hens' eggs. Both minor and major rings may be formed on the shell of an individual clam at any season of the year. In most eases the rings result Avhen the clam is disturbed, causing interruption of feeding and withdrawal of the mantle from the edge of the shell. When fceiling is resumed, the mantle is again extended, and secretion of the shell continues. Since the mantle, when re-extended, seldom aligns itself to the identical previous margin the new shell is not directly continuous with that in-eviously deposited but niiderlies the latter and projects beyond it forming a slightly raised ring. The color of this new portion may differ conspicuously from that of the adjacent portion of the shell. Thus the growth ring used in age determination is usually formed in the fall or winter months when the clam is subjected to the greatest prolonged period of disturbances, or during the spawning period. Many clams form rings when the,y continue growth after an injury (frequently the result of a clam fork piercing the mantle). This injury ring may appear on the shell as either a heavy circular ring parallel to the growth rings or as a disfiguration with a radiating scar running from the point of injury to the margin of the shell. Frequently, examination of the mantle of these injured clams will reveal seed pearls inbedded therein. These pearls are of no commercial value aiul are often so small. Figure 120. Inju
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