The holy Pontiff Felix III is a Pope of the fourth century. He was martyred in Tuscany in the time of the Arians (A.D. 365). He is sometimes referred to as Pope Felix II - there was a Pope Felix II in the earlier part of the fourth century, who is usually regarded as an antipope, and this causes confusion in enumeration.
Sapientiam sanctorum narrent populi, et laudes eorum nuntiet Ecclesia: nomina autem eorum vivent in saeculum saeculi. * Exsultate, justi, in Domino: rectos decet collaudatio.
Let the people show forth the wisdom of the saints, and the Church declare their praise: and their names shall live unto generation and generation. * Rejoice in the Lord, O ye just : praise becometh the upright.
(Ecclesiasticus 44:15,14 and Psalm 32:1 from the introit of Mass)
Praesta, quaesumus, Domine: ut, sicut populus christianus Martyrum tuorum Felicis, Simplicii, Faustini et Beatricis temporali solemnitate congaudet, ita perfruatur aeterna: et, quod votis celebrat, comprehendat effectu.
Grant, we beseech Thee, O Lord, that as Christian people rejoice in being able to celebrate the temporal solemnity of Thy martyrs Felix, Simplicius, Faustinus and Beatrice, so they may also rejoice thereat in life eternal and receive the fruit of the sacrifice which they offer.
From the Catholic Encyclopaedia.
On St Felix: http://www.newadvent.org/cathen/06030b.htm
On the Antipope Felix II: http://www.newadvent.org/cathen/06030a.htm
On SS Simplicius, Faustinus and Beatrice: http://www.newadvent.org/cathen/14003a.htm