Lost power during install of MATE: how to recover?

I tried to install MATE from Add/Remove Software, selecting MATE from the package collections. During the download/install there was a power outage. The result is something that is somewhat installed.

When I log in, MATE is one of the sessions available. If I use it, it seems to mostly work but it is broken. What does not work is gnome-terminal. A window comes up but there is no command prompt. The title bar looks OK and the menu bar works. But the window itself is empty. Gnome-terminal still works fine in xfce and gnome sessions.

Using Add/Remove Software I can't remove or install MATE. It comes up indicating it is not installed. If I select it and press Apply, nothing happens. How can I get rid of MATE so that I can install it cleanly?

Thanks
Jim