opisthopulmonate

from The Collaborative International Dictionary of English v.0.48

Opisthopulmonate \O*pis`tho*pul"mo*nate\, a.[Gr. 'o`pisqen
   behind + E. pulmonate.] (Zool.)
   Having the pulmonary sac situated posteriorly; -- said of
   certain air-breathing Mollusca.
   [1913 Webster]