

v % 





Figure 3. — Upper valve of a sea scallop taken from shallow water showing prominent annual rings. 



calcareous plate, can be easily picked out of the 

 resilifer. The plate can then be examined with a 

 low-power microscope or hand lens (fig. 8). If 

 the ligament has been lost, it is still possible to 

 examine the corresponding impression on the 

 resilifer. 



OTHER SHELL CHARACTERISTICS 



In some areas, annual invasions of boring or- 

 ganisms infect the upper valve of the sea scallop 

 (figs. 6 and 9). The areas of heaviest infestation 

 can be easily seen if the shell is held over a strong 



302 



light. The annual rings can usually be located 

 between the infected areas. The weight of the 

 shell is sometimes an index of rate of growth. A 

 thin shell is usually the sign of a fast growing 

 individual; a thick, heavy shell usually means 

 slow growth. Some shells exhibit areas of convex 

 curvature between the annual rings (fig. 10). The 

 profile of these shells, held at arm's length, show a 

 series of hills and valleys. The annual rings can 

 usually be found in the valleys. An occasional 

 shell, or sample of shells from particular areas, 

 will show changes in color pattern of an annual 



U.S. FISH AND WILDLIFE SERVICE 



