A three-year study was conducted to determine oviposition periods of the volutid gastropod Adelomelon brasiliana, the abundance and distribution pattern of its egg capsules in the region of Mar del Plata, Argentina. Results indicate that oviposition was correlated with water temperature. Reproduction occurred from September/October to May/June. Because egg capsules are not attached to the substratum and drift freely on the bottom along a narrow zone close to the shoreline, they can become stranded on the beach after storms, thus suffering mass mortality. This was reflected by a decline in snail recruitment during one study year in which storm surges were frequent and severe. The developmental stages of the egg capsules were characterized, and the proportion of early and late developmental stages determined monthly. This allowed an estimate of recruitment during each reproductive season. Twenty percent of the egg capsules at hatching contained one to three embryos that were considerably smaller than their siblings and 6% of the egg capsules at the same developed stage had one to four teratological embryos. Egg capsules laid down on the sea bottom showed an aggregated distribution pattern. The average developmental time was 57 ± 4 days. Protein and sugar concentration and pH of the intracapsular fluid decreased as embryo development progressed. Several proteins with different molecular weights were present in the intracapsular fluid during the entire intracapsular development.