pleuroperitoneum

from The Century Dictionary.

• noun A serous membrane, representing both pleura and peritoneum, which lines a pleuroperitoneal cavity, as in vertebrates below mammals.

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

• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy The pleural and peritoneal membranes, or the membrane lining the body cavity and covering the surface of the enclosed viscera; the peritoneum; used especially in the case of those animals in which the body cavity is not divided.