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}.