The Collaborative International Dictionary of English v.0.48:

Lagena \La*ge"na\, n.; pl. L. Lagen[ae], E. Lagenas. [L., a
   flask; cf. Gr. ?, ?.] (Anat.)
   The terminal part of the cochlea in birds and most reptiles;
   an appendage of the sacculus, corresponding to the cochlea,
   in fishes and amphibians.
   [1913 Webster]