Abstract
Summary The Australian Mud Whelk, Velacumantus australis, is common in certain places along the eastern and southern coasts of Australia. Two populations from Narrabeen Lagoon, near Sydney, were studied over the period of one year. Breeding takes place during the summer. Most snails probably breed for the first time at the end of their second year, many die during the next year, but some probably live into their fourth year. Details of the growth of juveniles, and changes in population structure with time, are given.