It may look like a paradox that the Patriarch isn't the Celebrant in this case.
The church of St.Mark's, in fact, was at that time the place where official State religious services in the presence of His Most Serene Highness the Doge of Venice and his court were celebrated.
Indeed, until the fall of the Most Serene Republic and the Napoleonic invasion of the Venetian States, the Cathedral of the city of Venice and seat of the Patriarch was the Basilica of San Pietro di Castello, which still bears the title of Co-cathedral.
The text gives also a clue about the so called "Marcian Rite", or Venetian Use of the Roman Rite, still used in Venice until the fall of the Republic.
EASTER SUNDAY
When the top of the Sepulchre has been revealed in the morning by the sacristan, and the Most Blessed Sacrament put in its place with due reverence, our clergy gathers in the Sacristy at the appointed hour; together with whoever is performing their duties under the guidance of the Master of Ceremonies. The Pala [The Pala d'Oro is the great golden altarpiece behind the high altar which is exposed only on major feastdays]having been opened at Prime, and the treasure correctly set out on the altar; four acolytes, wearing clean surplices, slowly leave the sanctuary carrying silver tapers.
The cross-bearers, however, wear new long white damask dalmatics and carry a large silver cross in their midst. They are followed by a host of junior clergy and priests, and behind them the subcanons and canons in order, wearing ceremonial vestments. Then the Reverend Vicarius or (if he is absent) the senior canon, in precious vestments, with three lighted candles which are to be distributed to His Most Serene Highness[the Doge], to the Procurator and to the Celebrant. Next follows the Master of Ceremonies, together with three members of the clergy, one of whom is to carry the Liber Ordinarius, and another the prayer-book for the reciting prayers at Prime at the appropriate time at the Sepulchre; the third is employed in the tasks of the very same Master of Ceremonies.
The procession thus formed goes out through the San Clemente door, and makes its way directly to the great staircase to the left below the loggia. It halts under the loggia of the upper Palace, with the choir drawn up on both sides. The Reverend Vicarius himself, accompanied by the Master of Ceremonies, climbs the stairs of the Ducal Palace, and meets His Most Serene Highness as he descends the stairs of the Collegium [The Doge is wearing is most solemn ceremonial vestments: the Ducal Crown called "Corno" with the "camauro", the purpule Ducal mantle with ermine, the "stocco", the puple slippers, the golden spurs, the collars of the Orders of the Most Serene Republic of Venice.]
First, after making due reverence, he offers a lighted candle to His Highness, a second candle to the Procurator of our church, who on the return journey goes back to his own place. The third candle is reserved to be offered to the Most Reverend Chief Priest [the"Primicerius"].
He, while the procession is taking place, must clad himself in pontifical robes near the Great Altar in order to celebrate solemn Mass, together with the same Ministers who served at the celebration of Maundy Thursday.
When these candels have been offered, the afore-mentioned clergy descend the great staircase from the Palace with extreme modesty and go out through the golden door (unless it is raining: for in that case they will make an entrance in the same order in which they came through the San Clemente door, and they will go to the Sepulchre via the small staircase of San Iacobe, for the seats prepared there for the sermon will have been removed previously). And when our cross enters the main square the bells are rung. (The Ducal bell, indicating the arrival of His Highness, cannot be rung in the morning, nor can His Highness be reminded of Easter Sunday by the Most Reverend Primicerius himself).
However, when the procession has reached the church, all advance to the second great doorway of the church which must remain closed, as well as the others, except the two small ones, one of which leads to the parsonage, and the other tothe altar of San Clemente. And when the choir has positioned itself between the two great doors in the Narthex of the church, which is the best place for its formation (for His Most Serene Highness also enters through the Nathex with the Most Illustrious Procurator and Most Illustrious Orators), the Reverend Vicarius approaches the closed door and knocks three times with the bronze ring hanging on the door, with three knocks on each occasion, so that thereb are nine knocks in total.
And the singers inside the church chant:
"Whom do you seek at the Sepulchre, O worshippers of Christ?"
And those outside the doors, singing from without, should reply:
"Jesus of Nazareth, Who was crucified, O worshippers of Haeven!"
And those within should proclaim:
"He is not here. He has risen from the dead, as was prophesied. Go forth and
proclaim this, saying that He has risen from the dead".
When this has been done, those who are inside continue:
"Come ye and see the place where the Lord was laid. Alleluia, Alleluia!"
But when they say "Come ye and see", the doors of the church are opened wide, and as they go in, the clergy process in order until they are opposite the Sepulchre.
But when His Most Serene Highness reaches the Sepulchre, he halts facing the Sepulchre.
Then the Reverend Vicarius climbs up to the Sepulchre, and, after looking to both sides, stands at the door of the Sepulchre (facing His Most Serene Highness) and sings:
"Christ has risen!"
To which the response is given:
"Thanks be to God!"
Then, descending the steps of the Sepulchre into the midst of the choir-members, he sings the same words, raising his voice slightly, and the choir should reply in the same way (as above).
He sings the same refrain a third time before His Most Serene Highness at a due distance, once more raising his voice. And when the same response has been given by the choir, he approaches His Most Serene Highness and kisses him, and then he kisses the Most Illustrious Procurator, saying:
"Christ has risen!"
And they reply:
"Thanks be to God!"
Then the Reverend Vicarius himself kisses the Canon nearest to him, who in turn similarly kisses another Canon who is nearest to him, and so on to the least senior Canon, each cleric who is present speaking and responding as above.
Then His Most Serene Highness with the Most Illustrious Senate walks up to the Chancel. The clergy remain at the Sepulchre (except for the singers of the cappella, who walk up into their pulpit to sing Mass) to say the Office of Prime.
"Officium Majoris Ebdomadae iuxta consuetudinem Ecclesiae S. Marci Venetiarum", 1597, ff. 280-285"(Engl. Transl. by Pauline Grundy).
