A google search revealed that "lion's tooth" refers to what's more commonly known as a Dandelion. "The common English name Dandelion is a derivation of the French Dent-de-Lion, (tooth of the lion), a reference to the deeply serrated edge of the leaves."
(from http://davesgarden.com/pf/go/885/index.html)
(from http://davesgarden.com/pf/go/885/index.html)