Figure 4. — Upper valve of a sea scallop taken from a heavily fished area, showing 

 malformation as a result of injury to the mantle. 



nature which may help to locate the rings (fig. 11). 

 Figures 9, 10, and 11 represent selected indi- 

 viduals; obviously, not all shells are so strikingly 

 marked. 



READING A SAMPLE 



The shells to be read must first be cleaned of all 

 foreign matter. It is best to soak them in a strong 

 solution of a nonbleaching detergent and then 

 scrub them with a wire brush. The length fre- 

 quency is determined to see if the sample is 

 polymodal. We define length for these purposes 

 as being measured along the greatest diameter of 

 the shell from umbo to opposite margin. Shells 

 that do not have a large number of shock rings 

 and appear to have prominent annual rings are 



then sorted out. The shells and resilia of these 

 individuals are studied first, and a preliminary 

 table of length at time of annual ring formation 

 is prepared. 



With this table as a guide to the most probable 

 location of the annual rings the rest of the sample 

 is read. It is best to work from the smaller to the 

 larger specimens. All of the clues mentioned pre- 

 viously are used as occasion demands and oppor- 

 tunity affords. The more difficult shells are set 

 aside until the last when the averages and the 

 deviations are more firmly established. These, as 

 well as the larger, older shells with the annual 

 rings near the margin crowded together, can 

 usually be best interpreted by reference to the 

 resilia. 



ANNUAL MARKS ON SHELL OF SEA SCALLOP 



303 



