In the case you described, the 1st Div. 8th Corps (which I think others correctly listed as white (rectangular) with red 6-pointed star might be the correct one the Alabamians saw (it could have looked square to them though it should have been a rectangle).

The 19th Corps shouldn't have had any red 4 pointed stars on their flags, though that would be the badge for their first division...though in neither of these cases would it be the "maltese cross"...not for another month or so.