1911 Encyclopædia Britannica/Monodelphia

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MONODELPHIA (i.e. “single uterus,” — in allusion to the fusion of at least the basal portions of this organ, and in contradistinction to their duality in the Didelphia, or Marsupialia), Cuvier's name for the group which includes all the orders of mammals (See Mammalia) except the Marsupialia and Monotremata; other titles for this group being Placentalia and Eutheria. With the Monotremata (q.v.) this group has no near affinity; and while more nearly related to the Marsupialia (q.v.), in which an imperfect allantoic placenta is sometimes developed, it is broadly distinguished therefrom by the invariable presence of a functional placenta by the aid of which the foetus is nourished throughout the greater portion of intra-uterine life. Other distinctive features by which marsupials are separated from monodelphians or placentals will be found in the article last mentioned. (R. L.*)