What does 'penes' mean here, and what does summa agree with? Chapter 55.4

[Phoebus Apollo]

ab hoc epigrammate coepit poetarum esse mentio diuque summa carminis penes Mopsum Thracem memorata est, donec Trimalchio 'rogo,' inquit 'magister, quid putas inter Ciceronem et Pub⟨li⟩lium interesse?

If I treat penes as the preposition 'belonging to' (and goes with Mopsum), and summa as the nt pl, and it forms a partitive genitive with carminis, I get: 'and for a long time the greatest part of the song/poem was said to belong to Mopsus of Thrace' - I'm not sure if this is right though.

 

[Glabrigausapes]

Perfectly right, my friend. Only for summa maybe 'the whole' or 'the entirety' is better (unless context says otherwise).

 

[Phoebus Apollo]

Perfectly right, my friend. Only for summa maybe 'the whole' or 'the entirety' is better (unless context says otherwise).

Thanks very much!