A letter of recommendation from a bishop (apostolium) was required from clerics who wished to travel to another diocese (see [371] and [376]). Since they were forbidden to leave their posts without the bishop's permission confirmed by these letters, it is quite understandable that they had no right to write this particular document themselves. However, there is the possibility that before this decree presbyters issued letters of recommendation to lower clergy (see discussion in [839].
Martyrarius was a cleric responsible for safeguarding the relics kept in the church. He also supervised their cult, for example by distributing the contact relicts among the pilgrims. This position could be held by a presbyter.