tetrapneumona

from The Century Dictionary.

• A division of Araneina, or true spiders, having four lungs, four spinnerets, and eight approximated ocelli: distinguished from Dipneumones.
• A group of holothurians, represented by the genus Rhopalodina, having four water-lungs (whence the name). Schmarda. Also called Decacrenidia, Diplostomidea, and Rhopalodinæ.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) 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.