This is the published version of a 2005 Freiburg doctoral dissertation, and consists of a detailed analysis of a manuscript of the Psalter in the Middle Egyptian dialect of Coptic and more than one hundred pages of appendices providing new editions of two Greek Psalter manuscripts from the seventh and fourth centuries respectively. The main object under consideration is a fourth- or fifth-century parchment codex (hereinafter M), which consists of 498 written sides and was discovered in 1984 under the head of the mummy of a young girl within a necropolis at al-Mudil, 45 km north of Oxyrhynchus. This manuscript is now in Cairo and was published in 1995. Its text is analysed by Emmenegger using a number of different methods, including comparison with various witnesses and versions and an investigation of translation technique. M's textual affinity is variously characterised as being close to Papyrus Bodmer XXIV, agreeing frequently with Sahidic and/or Bohairic but depending only on the former, containing Hexaplaric and Lucianic readings, having no direct influence from the Hebrew Psalter (MT or 11QPs^a), yet being based on a Vorlage revised according to the Hebrew. The Middle Egyptian version is thus geographically and textually in the middle of the other Coptic versions. The sheer diversity of textual affinity, combined with the facts that M shows few features not attested in other Coptic versions and that M's Vorlage seems to have differed in few points from known Greek texts, leads the author to conclude that the version may have been an attempt to find a mediating position between other texts, or an ‘Einheitsübersetzung’. The version is not, however, significantly older than the manuscript itself. Comparison between M and Middle Egyptian manuscripts of the New Testament (Matthew, Acts, Paul) reveals M's dependence upon the Middle Egyptian New Testament, and leads the author to conclude that there is some overall unity to these Middle Egyptian biblical texts. Comparison between M and the Coptic New Testament versions shows that the Psalter was influenced by Christian scribal activity. One allegedly discovered scribal action was the removal of the phrase ‘from the tree’ after ‘the Lord reigns’ in Psalm xcvi [xcv].10, a fact which might be used to provide a slight vindication of Justin Martyr's comments on this text. The history of the Egyptian Bible in this period is poorly understood; this meticulous study contributes significantly to our knowledge in this area.