In the modern Roman Rite, to-day is the optional memorial of St Peter Claver, Jesuit Apostle of the Slaves, while in the older Form, it is a feria with commemoration of the martyr St Gorgonius: in both cases, either the ferial Mass may be said (with commemoration in the Extraordinary, without it in the Ordinary), or Mass of the saint; the difference is that in the modern Divine Office, St Peter Claver's full Office may be read ad lib., whereas in the Breviary, only a commemoration is made of St Gorgonius at Lauds.
All that is known of this Gorgonius (there is another more famous Martyr of this name who died at Nicomedia at the outset of the Great Persecution of Diocletian) is that he died for the Faith sometime in the 3rd century, and was buried at the spot named "the two laurels" on the Labican Way; by Pope Gregory IV, his relics were transferred to St Peter's (where I hope to venerate them).
St Peter Claver (1580-1654), meanwhile, is a most amazing saint, a saviour of men after the model of Our Lord, whose indefatigable care for the bodies and souls of the poor African slaves brought into Cartagena (now in Colombia) caused him to so preach Christ and baptize in His Name that 300,000 - yes! even the modern Martyrology with its severe critical spirit attests to this! - received the laver of regeneration at his hands.
All this was summarized in his famous vow: Æthiopum semper servus (Ever the slave of the Ethiopians, or the African slaves).
Meanwhile, back in his religious community, he was the innocent victim of persecution from his fellow Jesuits, which only added to the severe penances with which he macerated his flesh - such as wearing a fearsome crown of thorns while studying in his cell, and also each morning before the rest awoke, when, shouldering a life-sized Cross, he lived out the last steps of Christ to Calvary by dragging this painful burden from his cell to the chapel (no wonder the other Jesuits complained!).
He died on Our Lady's birthday, hence, most appropriately, his feast is appointed for the day after pro aliquibus locis (and presumably for the Society of Jesus). There would be no reason why a Traditional Mass could not be said in his honour on the 9th (so long as St Gorgonius was commemorated if it were a Low Mass, juxta rubricas). Indeed, if the liturgical reform had not occurred, it would seem probable that his feast would eventually have been extended to the whole world, with St Gorgonius as his companion. Here is his collect from the Traditional Missal, and - modified - from the Novus Ordo:
TRADITIONALDeus, qui abreptos in servitutem nigritas ad agnitionem tui nominis vocaturus, beatum Petrum mira in eis juvandis caritate et patientia roborasti, ejus nobis intercessione concede, ut, quæ Jesu Christi sunt* quærentes, proximos opere et veritate diligamus. Per eumdem...(God, Who intending to call the negroes abducted into slavery to the knowledge of Thy Name, didst strengthen blessed Peter with wonderful love and patience in aiding them: grant to us by his intercession that, seeking what things are Jesus Christ's*, in work and truth we may love our neighbours. Through the same...)NOVUS ORDODeus, qui beatum Petrum servorum servum effecisti eumque mira in eis juvandis caritate et patientia roborasti, ejus nobis intercessione concede, ut, quæ Jesu Christi sunt*, quærentes, proximos opere et veritate diligamus. Per [eumdem]...(God, Who didst make blessed Peter the slave of the slaves, and didst strengthen him with wonderful love and patience in aiding them, grant to us by his intercession that, seeking what things are Jesus Christ's*, in work and truth we may love our neighbours. Through...)
* Cf. Philippians ii, 21: "For all seek the things that are their own:
not the things that are Jesus Christ's".
Note that the Novus Ordo is a little shy of referring to the trapped and enslaved negroes, and prefers a play on words (servant of servants, slave of slaves), which unfortunately loses the great focus of the Traditional prayer on the signal work of St Peter, not just in patiently and charitably serving them, but above all in baptizing so many to be made sons of God and co-heirs with Christ, that they might inherit life eternal. There are too many instances of such a this-worldly focus in modern prayers...
(If it were desired to read the Breviary, keeping his feast, all would be from the Common of Conf's-non-Pont's, but for his proper prayer.)