Transform Boundaries The final type of boundary is one where the two plates slide against each other in a sideways motion. These boundaries between plates is referred to as transform boundaries.
The three regions of the body of the Mollusk are the head-foot, the visceral mass, and the mantle-shell.
Mollusks usually build their shells in a trio of layers. The outermost band, the periostracum, derives mostly from protein, chiefly quinone-tanned protein but also some chitin, which makes up only a very small proportion of the total shell material. The inner layers are calcium-carbonate material.