zygodocieds: this group is second group which is seen both Mesozoic and Cenozoic too. They are oval coccoliths which have a proximal wall from are or two cycles from felsic fragments and it has a very thin internal proandimal. Structure of central area may be as a simple line or as a shape or more ecomplicated shapes Main structure of shields are similar to each other in two Eiffellithaceae (Mesozoic )and zygodiscaceae (mainly Cenozoic ) but in first one , it may show a pedicle in central structure . Famous genus of Mesozoic and Cenozoic are shown in fig 20.