Pteroceras

from The Collaborative International Dictionary of English v.0.48

Pteroceras \Pte*roc"e*ras\, n. [NL., fr. Gr. ? a wing + ? a
   horn.] (Zool.)
   A genus of large marine gastropods having the outer border of
   the lip divided into lobes; -- called also {scorpion shell}.
   [1913 Webster]