Micallef's Study on Trochid Molluscs

These data support Broekhuysens's earlier study on gastropods except that Calliostoma zyzyphinum appears to be more resistant to desiccation than its zonational position would suggest it ought to be. It has been suggested that some other factor, like maybe temperature tolerance, is at play here.

Similarly, Monodonta has a zonational range which overlaps with that of Gibbula umbilicalis but is clearly much less resistant to desiccation than the latter. This is explained by the fact that the Gibbula sp. tends to be found in rock pools high on the shore and is thus not so exposed to desiccation as its zonational level might suggest.