Note 35
Transversa X literâ, summo capite circumflexo, Christum in scutis notat. Cacilius de M. P. c. 44. Cuper (ad M. P. in edit. Lactant. tom. ii. p. 500) and Baronius (A.D. 312, No. 25) have engraved from ancient monuments several specimens - as thus, engraved ancient monograms
or engraved acient monograms of these monograms, which became extremely fashionable in the Christian world.
Note to Chapter 20 of DECLINE & FALL by Gibbon