Relation between theZ=64Shell Closure and the Onset of Deformation atN=88−90

The systematics of the onset of deformation in the $N=88-90\mathrm{}$ region is reexamined in light of the recently discovered shell closure at $Z=64\mathrm{}$. It is shown that the microscopic explanation of the origin of deformation already proposed for the $A\sim 100$ region is equally applicable here and leads to a new interpretation of the $A\sim 150$ region.