When the upper and lower teeth occlude (fit together), the pseudotalonid acts as a receptacle for cusp Y of the upper molar. Cusp Y is often termed the "pseudoprotocone" in this relationship.
When the upper and lower teeth interlock (fit together), the pseudotalonid acts as a socket for cusp Y of the upper molar. Cusp Y is often referred to as the "pseudoprotocone" in this context.