to an endogenous rhythm of shell formation
rather than some exogenous factors, i.e. diurnal ¯uctuations,
tide, or current ¯ow. Richardson (1991) and
Gaspar et al. (1995) showed in a series of experiments
with continuously immersed clams that the total
number of bands in the shell was correlated with
the growth of the shell rather than with daily or tidal
control. Therefore, bands cannot be used in this
species to measure tidal or daily growth rates.