Measuring decay rates of shells in a terrestrial environment should also take into account the bioeroding effects of land snails that use empty shells as a source of calcium for their own shell formation. This amounted to 30% shell weight loss in only two months in my experiment published earlier and was much higher than the 2 to 10% decay in one year measured in nylon mesh bags published recently (Ilarri et al. 2015). This bioerosion is not measured when shell decay on land is studied by placing the decaying shells in nylon mesh bags which living gastropods cannot enter freely. Moreover, shell crushing predators (birds, rats) also play an important role in shell decay. That decay in aquatic environments is 6- 12 times higher than on land as published by Ilarri et al. (2015) can be questioned.