The Effect of Rock Type on Shore Organisms
Lewis suggests that the nature of the underlying rock on a shore is a 'minor factor' in controlling distribution of the organisms. There are, for example, molluscs and annelids which can burrow into softer rock, these are not going to be abundant on a shore in which the underlying rock is granite.
Another important factor may be the way in which some rocks will hold water better than others, or provide more crevices. Lewis again considers all of this may have some effect on abundance but unlikely to have much importance in distribution.