Extraembryonic membrane formed by the fusion of the allantois and chorion. ... (05 Mar 2000) ... 
(ә-lan″to-kor´e-on) the allantois and chorion as one structure.
Type: Term Pronunciation: ă-lan-tō-kōr′ē-on Definitions: 1. Extraembryonic membrane formed by the fusion of the allantois and chorion.