The Collaborative International Dictionary of English v.0.48:

Endognath \En"dog*nath\ ([e^]n"d[o^]g*n[a^]th), n. [Endo- + Gr.
   gna`qos the jaw.] (Zo["o]l.)
   The inner or principal branch of the oral appendages of
   Crustacea. See Maxilla.
   [1913 Webster]