Can't specify options to show or hide for a select list which depends on another

I have two select widgits, the field "riding" is dependent on the field "jurisdiction". After creating a dependency between the two, I go to edit the dependency. I get a pull down menu labeled Jurisdiction with the correct allowed values. But under it I get "No options available", not even a label "riding".

I thought initially it might be the number of options under riding (there were 438). But after reducing the allowed values for riding and re-creating the dependency, the bug persists.