In the Bibliothèque Interuniversitaire de Montpellier a manuscript is present which is a 15th century copy of the “Justiniani institutiones” . The Corpus Juris (or Iuris) Civilis (“Body of Civil Law”) is the modern name for a collection of fundamental works in jurisprudence, issued from 529 to 534 by order of Justinian I, Eastern Roman Emperor. It is also sometimes referred to as the Code of Justinian, although this name belongs more properly to the part titled Codex Justinianus.
The work as planned had three parts: the Code (Codex) is a compilation, by selection and extraction, of imperial enactments to date; the Digest or Pandects (the Latin title contains both Digesta and Pandectae) is an encyclopedia composed of mostly brief extracts from the writings of Roman jurists; and the Institutes (Institutiones) is a student textbook, mainly introducing the Code although it has important conceptual elements that are less developed in the Code or the Digest. All three parts, even the textbook, were given force of law. They were intended to be, together, the sole source of law; reference to any other source, including the original texts from which the Code and the Digest had been taken, was forbidden. Nonetheless, Justinian found himself having to enact further laws and today these are counted as a fourth part of the Corpus, the Novellae Constitutiones (Novels, literally New Laws). 
The manuscript starts (f. 001r) with a decorated page, with – in the lower right corner – a malacomorph hybrid. This hybrid has two sinistral shells, one as a cap, the other as lower body. Both shells have a few coils only and are stylised. The hybrid is winged, reminding of a similar figure, e.g. in item #45.
The second occurrence of a snail is on f. 023v, where in the lower border a snail opposes a frog. The dextral shell is somewhat stylised, with the aperture widening. The animal has two tentacles and is humanised, with an eye and a grim expression on its ‘face’.
On f. 107v an interesting variation on the theme ‘knight v. snail’ is seen. The knight has a sword above his head in his right hand, ready to attack. In his left hand he holds a shield which, however, appears a mirror. The snail has a rather perplexed expression, but nevertheless sees a smiling face in the mirror. The stylised shell is sinistral, with relatively many whorls and an undulating apertural lip. The animal has two tentacles pointing forward, and an eye-spot.
The interesting thing is here the positioning of the snail on a tree trunk. Wait and see this happen again…
 BIM Ms. H 418. http://www.calames.abes.fr/pub/#details?id=D01041914. See also http://bit.ly/1fs9zwL for instructions how to access the illuminations.