Nam mihi nihil novi potest afferri, sicut ille fer[i]culus †ta mel habint praxim†.

If we take ta mel and habint as a corruption of tamen and habuit, we can tentatively read this sentence as: “For nothing new can be brought to me, as that dish has nonetheless proved”. In the context of his speech, the implication is that Trimalchio, no longer entertained by the delights of a feast, must turn to philosophizing.

This sentence, however, is contentious for several reasons:

1. There is some disagreement as to whether fer[i]culus should be read as fericulum (“that wild thing”) or ferculum (“dish”). The latter makes more sense in the context of the course previously served.
2. Ta mel has also been construed as corruptions of iam semel (which doesn’t match Trimalchio’s exaggerated show of refinement, because it would imply that the dish had been served before and that Trimalchio allowed it to be served again), camella (“goblet”; Trimalchio has just invited his guests to have a drink), or tam el[egans] (in reference to the dish).
3. Praxim comes from the Greek praxis (“good result”, “success”, “action”, “business”), which doesn’t really translate to “proof”. This has led Brent Vine to hypothesize that praxim ought to be taken as taxim, from the Greek taxis (“arrangement”) (Vine, 130). This would translate to “just as that dish had a [careful] arrangement”.