I found this-
Dagon, the fish-god, represented that deity as a manifestation of the same patriarch who had lived so long in the waters of the deluge. As the Pope bears the key of Janus, so he wears the mitre of Dagon. The excavations of Nineveh have put this beyond all possibility of doubt. The Papal mitre is entirely different from the mitre of Aaron and the Jewish high priests. That mitre was a turban. The two-horned mitre, which the Pope wears, when he sits on the high altar at Rome and receives the adoration of the Cardinals, is the very mitre worn by Dagon, the fish-god of the Philistines and Babylonians. There were two ways in which Dagon was anciently represented. The one was when he was depicted as half-man half-fish; the upper part being entirely human, the under part ending in the tail of a fish. The other was, when, to use the words of Layard, "the head of the fish formed a mitre above that of the man, while its scaly, fan-like tail fell as a cloak behind, leaving the human limbs and feet exposed." Of Dagon in this form Layard gives a representation in his last work; and no one who examines his mitre, and compares it with the Pope's as given in Elliot's Horoe, can doubt for a moment that from that, and no other source, has the pontifical mitre been derived. The gaping jaws of the fish surmounting the head of the man at Nineveh are the unmistakable counterpart of the horns of the Pope's mitre at Rome.I don't know if there is truth to this but it seems strange. His ring is called " the Fisherman's ring" and people kiss it. Why? This is even stranger.
