Using the curves you have created in the initial post and the curve from the isoparm at the end of the surface you can do 4 boundary surfaces which can be rebuilt and attached.

This will create kind of a reshaped half nurbs sphere at the end of the surface. The down side to this is you will have a pole at each end.

Here is the idea...

The curves are numbered 1-8. The boundary surfaces are created by picking the curves in the order shown. (ie the top front surface is a boundary formed from curve 1, 2 and 4 (1-2-4). The order you select the boundary curves in is important the pole will be between the first two curves selected.

After creating the four surfaces (and rebuilding them) attach them to create a single surface.