The Collaborative International Dictionary of English v.0.48:

Glass-snake \Glass"-snake`\, n. (Zool.)
   A long, footless lizard (Ophiosaurus ventralis), of the
   Southern United States; -- so called from its fragility, the
   tail easily breaking into small pieces. It grows to the
   length of three feet. The name is applied also to similar
   species found in the Old World.
   [1913 Webster]