Dear Carol;-
    Clench & Turner (Jonsonia #31) spell it "pourtelesii". The other
one is "celesti". Another example of similar shells from different
places is E. zelebori Dunker, 1866 from (where else?) NZ; and E.
blainei C&T, 1953 uncommon from Florida. There are no distinguishing
characteristics in the two shells. DNA studies may prove different,
but I don't know of anyone doing such work.
   Art