It’s easy enough to get lost during the long silent Canon, when there are relatively few cues to alert the congregation to whether father is on Clement, Cletus, or Anastasia (something most Catholics are accustomed to being able to know by listening). To make matters more confusing, however, there is often an exchange between the servers and priest that is likely not in one’s hand missal or missalette. This is the so-called “Second Confiteor,” a second instance of the confiteor found in the prayers at the foot of the altar, but recited immediately before the Domine non sum dignus. It was deleted, without explanation or reprobation, from the 1962 typical edition of the Missale Romanum (although it remains in the rite for the Ordination Mass in the 1962 Pontificale Romanum).
Most commentators seem to regard the Second Confiteor as a legitimate custom in the celebration of the Extraordinary Form. Fr. Zuhlsdorf expresses this opinion, as do the Canons Regular of St. John Cantius. I mention it in this space purely for informational purposes and for the sake of combating confusion.