ORGANISMS ASSOCIATED WITH BURROWING WHELKS OF THE GENUS BULLIA

Organisms found associated with the psammophilic neogastropod Bullia i nclude hydroids, a boring sponge and algae which grow on, and burrow i nto, the shell. The shell may also be the recipient of the egg capsule s of other species of gastropods. Peridinian ciliates are commonly fou nd attached in some numbers to the tentacles and an occasional rotifer occurs on the soft parts of the animal. The gut is rich in bacteria, some of which are symbiotic. Digenetic trematode larvae are the most c ommon internal parasites and larval cestodes also occur. Preliminary d escriptions are given of two apparently new trematode larvae and of a cestode cysticercoid. A nematode worm is occasionally present in the g ut. The absence of external parasites is noted and it is suggested tha t the shells of the whelk represent a refuge for smaller organisms or their eggs in an unstable environment lacking geological diversity.