Another feast dropped from the calendar before Vatican II.

http://en.wikipedia.org/wiki/Pope_Leo_II

It's worth reading, and in the Missal/Breviary under Pope St. Pius X.  Anyone have anything else?

I find this part interesting:

During this council, Pope Honorius I was anathematised for his views in the Monothelite controversy as tolerant of heresy.[4] Leo took great pains to make it clear that in condemning Honorius, he did so not because Honorius taught heresy, but because he was not active enough in opposing it. In accordance with the papal mandate, a synod was held at Toledo (684) in which the Council of Constantinople was accepted.[4]

Regarding the decision of the council, Leo wrote once and again in approbation of the decision of the council and in condemnation of Honorius, whom he regarded as one who profana proditione immaculatem fidem subvertare conatus est (roughly, "one who by betrayal has tried to overthrow the immaculate faith"). In their bearing upon the question of papal infallibility these words have caused considerable attention and controversy, and prominence is given to the circuмstance that in the Greek text of the letter to the Emperor which the phrase occurs, the milder expression subverti permisit ("allowed to be overthrown...") is used for subvertare conatus est.[4]

Referring to the defection of Pope Honorius and to Monothelism as a continuation of Monophysism, Dom Guéranger made this prayer to St. Leo II:

"What craft was displayed by Satan in this campaign prolonged for two centuries, noiselessly, the better to secure success. What exultation rang through the abyss when one sad day saw the representative of Him who is the essential Light appear to side for a moment with the powers of darkness! A cloud seemed to have come between Heaven and those mountains of God, where He dwells with His Vicar; it is probable that the social aid of intercession was weaker just then than it should have been.

 "Be ever at hand, O Leo, to ward off all similarly dangerous situations. Uphold, in every age, the Pastor who rules Christ’s Church, that he may keep himself aloof from the darkening mists that earth exhales. Keep ever alive in the hearts of the faithful flock that strong prayer, which should continually be made without ceasing for him by the Church; and then Peter, were he even chained in the depths of the darkest dungeon, will be reached by the Sun of Justice and clearly see his way in the pure ray; then will the whole body of the Church be filled with light."

Here is more on Pope St Leo;
 Sicilian versed in Latin and Greek, St. Leo II was elected to the papacy in 681. Emperor Constantine IV Pogonatus did not confirm his election until 682, when Leo was consecrated. He ratified the decisions of the sixth ecuмenical council (680) and condemned Honorius I's stand on monothelitism. During Leo's reign, the emperor returned control of Ravenna from the exarch to the emperor; to soften the blow, Leo exempted the see of Ravenna from the customary consecration taxes. Leo had a been singer trained in the papal choir school. He died in 683.

http://catholic.org/saints/saint.php?saint_id=1002

He was a Sicilian by birth (the son of a man named Paulus), and succeeded Agatho. Though elected pope a few days after the death of St. Agatho (10 January 681), he was not consecrated till after the lapse of a year and seven months (17 August 682).[1] Leo was known as an eloquent preacher who was interested in music, and noted for his charity to the poor.[2]

Elected shortly after the death of Agatho, Leo was not consecrated for over a year and a half. The reason may have been due to negotiations regarding imperial control of papal elections.[3]

These negotiations were undertaken by Leo's predecessor Agatho between the Holy See and Emperor Constantine IV. They concerned the relations of the Byzantine Court to papal elections. Constantine had already promised Agatho to abolish or reduce the tax that the popes had had to pay to the imperial treasury on their consecration over the course of about a century.[1]

Leo's short-lived pontificate did not allow him to accomplish much, but there was one achievement of major importance: he confirmed the acts of the Sixth Ecuмenical Council (680–1). This council had been held in Constantinople against the Monothelite controversy, and had been presided over by the legates of Pope Agatho. After Leo had notified the Emperor that the decrees of the council had been confirmed, he made them known to the nations of the West. In letters written to the king, the bishops, and the nobles of Spain, he explained what the council had effected, and he called upon the bishops to subscribe to its decrees.[1]

During this council, Pope Honorius I was anathematised for his views in the Monothelite controversy as tolerant of heresy.[4] Leo took great pains to make it clear that in condemning Honorius, he did so not because Honorius taught heresy, but because he was not active enough in opposing it. In accordance with the papal mandate, a synod was held at Toledo (684) in which the Council of Constantinople was accepted.[4]

Regarding the decision of the council, Leo wrote once and again in approbation of the decision of the council and in condemnation of Honorius, whom he regarded as one who profana proditione immaculatem fidem subvertare conatus est (roughly, "one who by betrayal has tried to overthrow the immaculate faith"). In their bearing upon the question of papal infallibility these words have caused considerable attention and controversy, and prominence is given to the circuмstance that in the Greek text of the letter to the Emperor which the phrase occurs, the milder expression subverti permisit ("allowed to be overthrown...") is used for subvertare conatus est.[4]

At this time Leo put an end to the attempts of the Ravenna archbishops to get away from the control of the Bishop of Rome. The Pope sweetened the deal for the Ravenna bishops by abolishing the tax it had been customary for them to pay when they received the pallium.[5]

Also, in apparent response to Lombard raids, Leo transferred the relics of a number of martyrs from the catacombs to churches inside the walls of the city. He also dedicated two churches, St. Paul's and Sts. Sebastian and George.[5]

Leo was originally buried in his own monument; however, some years after his death, his remains were put into a tomb that contained the first four Pope Leos.[6]

http://en.wikipedia.org/wiki/Pope_Leo_II