In the Palissy database of the French Ministry of Culture I found a curious snail sculptured on a tomb in the Saint Taurin church in Évreux (Dept. Haute Normandie, France). It is dated from the 13th century. 
The snail is seen from the dorso-lateral side, the dextral shell with growth striae visualised as riblets. The head is human, but the face is damaged. Given the size and general appearance of the snail, it may have been inspired on Helix pomatia (Linnaeus, 1758) if one assumes the sculpture was made within the region.
The disproportionally enlargement of snails, like in this case (but cf. the picture in the heading of this site), has already been noted by Pinon  and has been associated with warfare.
 http://bit.ly/1aMsmUR (figure from Wikicommons; 23.i.2014).
 Pinon, R. (1980). From illumination to folksong; the armed snail, a motif of topsy-turvy land. In: Newall, V.J. (ed.), Folklore studies in the twentieth century. Proceedings of the Centenary Conference of the Folklore Society: 76–113. Boydel & Brewer, Woolbridge / Rowman & Littlefield, Totowa. See p. 84–85.