EXPLANATION OF PLATE V. 
Fig. 1. Lower (left) valve of Ostrca cuculata; (Born) d, dorsal edge, 
v , ventral ditto, a , anterior margin, p, posterior ditto, showing 
a large blister with the opening of the worm tube on the 
anterior margin. 
„ 2. Upper (right) valve exhibiting two blisters ; the one with a dotted 
outline near the ventral edge, is covered by a calcified layer ; 
the other is in the membranous stage. 
„ 3. Upper valve showing a larger blister, the work of a single worm 
(right hand figure). The same with the surface of the blister 
removed showing the position occupied by the worm (left 
hand figure). 
