Medieval Meme: Knight vs Snail

It was a thing, apparently.  On the British Library's Medieval Manuscripts blog, Sarah Biggs writes:

We were examining ... an English roll from the last part of the 13th century..., when one of our post-medieval colleagues noticed a painting of a knight engaging in combat with a snail. ... This struck him as odd, which struck the medievalists in the group as odd; surely everyone has seen this sort of thing before, right?  

She notes, however, that "the ubiquity of these depictions doesn’t make them any less strange" -- especially since "the knight is often depicted on the losing end of this battle"!

For an assortment of images and theories, perhaps start with:

• http://sforsnail.blogspot.com/2010/07/medieval-snails.html
• http://medievalscribbles.blogspot.com/2012/05/historian-and-snail.html
• http://www.gotmedieval.com/2009/07/whats-so-funny-about-knights-and-snails.html
• http://blogs.smithsonianmag.com/smartnews/2013/10/why-were-medieval-knights-always-fighting-snails/