\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}.