Source : Webster's Revised Unabridged Dictionary (1913)

Tetraneumona \Tet`ra*neu"mo*na\, n. pl. [NL. See {Tetra-}, and
   {Pneumo-}.] (Zo["o]l.)
   A division of Arachnida including those spiders which have
   four lungs, or pulmonary sacs. It includes the bird spiders
   (Mygale) and the trapdoor spiders. See {Mygale}.