The inscription painted on crumbling stucco in the Mithraeum under Santa Prisca has provoked much discussion.
This image comes from Martin Vermaseren, The excavations in the Mithraeum of the Church of Santa Prisca in Rome, p.215 in the Google preview. It’s a diagram, not a plate; although apparently plate LXVIII shows it.
These are lines 13-15 of the inscription. The restored reading is:
Primus et hic aries astrictius ordine currit;
Et nos servasti eternali sanguine fuso;
Offero ut fiant numina magna Mithre.
On p.222 Vermaseren asks:
Finally there is the question whether the three lines of verse on this section of the wall (of which line 15 is the last) are related. … This is not at all certain, although it cannot be excluded.
It takes little effort to see that line. 14, “Et nos servasti eternali sanguine fuso” is indeed a restoration, rather than simply reading the text. Unfortunately Vermaserens discussion of the line on p.217-8 is not online.