Give differences between the lancelet and lamprey regarding gill slits?

Lancelets commonly called amphioxus are marine living, small, eel like animals that belong to the subphylum cephalochordata. They have bilateral symmetry, triploblastic origin of organs and true coelom. The characteristic feature of lancelets is the presence of mayomers (unit of muscles).

The lampreys or lamper eel are slimy, eel like predators found in marine or freshwater. They have bilateral symmetry, triploblastic tissue organization and true coelom. They  are jawless aquatic animals with the presence of a suctorial disc with teeth as the feeding organs.