Τοῦ δὲ Πέτρου μαρτυρήσαντος παρῆλθεν εἰς Ἀλεξάνδρειαν ὁ Μάρκος κομίζων καὶ τα ταυτοῦ καὶ τὰ τοῦ Πέτρου ὑπομνήματα, ἐξ ὧν μεταφέρων εἰς τὸ πρῶτον αὐτοῦ βιβλίον τὰ τοῖς προκόπτουσι περὶ τὴν γνῶσιν κατάλληλα συνέταξε πνευματικώτερον εὐαγγέλιον εἰς τὴν τῶν τελειουμένων χρῆσιν or Τοῦ δὲ Πέτρου μαρτυρήσαντος παρῆλθεν εἰς Ἀλεξάνδρειαν ὁ Μάρκος κομίζων καὶ ταταυτοῦ καὶ τὰ τοῦ Πέτρου ὑπομνήματα, ἐξ ὧν μεταφέρων εἰς τὸ πρῶτον αὐτοῦ βιβλίον τὰ τοῖς προκόπτουσι περὶ τὴν γνῶσιν κατάλληλα συνέταξε πνευματικώτερον εὐαγγέλιον εἰς τὴν τῶν τελειουμένων χρῆσινταταυτοῦ [MS, PV] τα ταυτοῦ [AT]
In this context, "τα ταυτοῦ" seems to make more sense grammatically.
"Τοῦ δὲ Πέτρου μαρτυρήσαντος παρῆλθεν εἰς Ἀλεξάνδρειαν ὁ Μάρκος κομίζων καὶ τα ταυτοῦ καὶ τὰ τοῦ Πέτρου ὑπομνήματα..."
Here, "τα ταυτοῦ" refers to the memoranda of Mark, and "τὰ τοῦ Πέτρου" refers to the memoranda of Peter.
The phrase "τα ταυτοῦ" means "those of Mark," indicating possession or association, while "τὰ τοῦ Πέτρου" means "those of Peter."
So, in this sentence, "τα ταυτοῦ" makes more sense grammatically because it properly denotes the memoranda belonging to Mark.
