$\begin{array}{1 1} (a)\;\text{Fossil X was found in
deeper sedimentation.} \\ (b)\;\text{Fossil Y was found in deeper
sedimentation} \\ (c)\;\text{Fossil Y has homologus and
analogus organs of X} \\ (d)\;\text{Fossil Y has some vestigial
organs functional in X} \end{array} $
