Pietro Andrea Mattioli (1501–1577) was a doctor and naturalist born in Siena, Italy. He received his MD at the University of Padua in 1523, and subsequently practiced the profession in Siena,Rome, Trento and Gorizia, becoming personal physician of Ferdinand II, Archduke of Further Austria in Prague, and of Maximilian II, Holy Roman Emperor in Vienna. A careful student of botany, he described 100 new plants and coordinated the medical botany of his time in his Discorsi (“Commentaries”) on the Materia Medica of Dioscorides, which was also translated in several other languages. In this work, the woodcuts were of a high standard, e.g., allowing recognition of the plant even when the text was obscure [1, 2].
We find on one of the pages a woodcut of fungi with a snail .
This snail is indeed quite well illustrated, with both large and small tentacles. It may have been inspired by a Helix-like species. And the dextral shell is printed in a correct way!
 Petri Andreae Matthioli senensis, serenissimi Principis Ferdinandi Auchiducis Austriae &c. Medici, commentarii secundo aucti, in libros sex Pedacii Dioscoridis Anazarbei de medica materia. Venetiis, pp. Permalink: urn:nbn:de:hbz:061:2-171031.
 http://wellcomeimages.org/indexplus/image/L0039153.html via europeana.eu.