\Pleu`ro*per`i*to*ne"um\, n. [Pleuro- +
peritoneum.] (Anat.)
The pleural and peritoneal membranes, or the membrane lining
the body cavity and covering the surface of the inclosed
viscera; the peritoneum; -- used especially in the case of
those animals in which the body cavity is not divided.
Note: Peritoneum is now often used in the sense of
      pleuroperitoneum, the pleur[ae] being regarded as a
      part of the peritoneum, when the body cavity is
      undivided.