FISHERY BULLETIN: VOL. 82, NO. 1 







Fl( (URE 5 .— (a) Optical photomicrograph (compound microscope) of an acetate peel at a notch-mark in the ocean quahog, 

 Arctica islandica, shown in Figure 2 (scale bar = 100 jum). Note the single annual increment of growth formed laterally 

 beyond the notch-mark, (b) SEM photomicrograph of the same shell specimen (scale bar = 100 ;iim). Abbreviatons of 

 shell microstructural terms in this and subsequent figures are expalined in this text, (c) Transitional CA-CL microstruc- 



