Placencia, Placensia

I have just become aware that FamilySearch.org makes a distinction between
the "...cia" and the "...sia" forms of this name. It is my impression that
these names are interchangeable. The first "c" is sometimes an "s", but
that passes the "exact spelling:off" screen, but not the second "c" or "s".
Basically, that means one has to look-up both forms of the name when
researching.