See Fr. Z’s latest entry on his blog:
…And who knows if, at last, during pontifical Masses, there won’t return to view next to the Pontiff the Cardinal Protodeacon and the second Cardinal in the diaconal order. Just as once upon a time. Just as it ought to be again today.
Remember, a lot of what I learned about the Curia can be blamed on Henry Morton Robinson…
Is the Protodeacon the senior Cardinal?