In the Bodleian Library, Oxford, one of the manuscripts is made by various authors including Lambert le Tort and Alexandre de Bernai (de Paris). The manuscript originated in 1338–1344 in Tournai and is considered Flemish. It describes the “Romance of Alexander [the Great]” [1, 2].
On folio 027v the text concerns the Foray of Gadres (Gaza), and in between the two columns a boy with a large snail on top of his head can be seen.
The snail is clearly a dextral specimen with a regularly coiling shell. Nothing seems coming out of the aperture; but then, what are those two pointed bat-like ears on top of the shell?
 BLO, Ms. Bodl. 264, part 1, 100 ff. http://to.ly/GpEn.
 See also http://en.wikipedia.org/wiki/Alexander_romance, especially under French versions, sub 5.