A new representative of the incertae sedis Cornulitidae is described from the Devonian of the western part of the Armorican massif (rade de Brest, Kerdreolet Formation, upper Emsian, patulus Zone). Reticornulites reticulatus n. gen., n. sp. is distinguished by a curved and flexuous conical shell, free of attachment(?), with a very typical reticulate ornamentation with predominant transverse rings and fine longitudinal striae. Specimens preserved as internal moulds and external casts; structure and microstructure unknown.Original Abstract: Une nouvelle forme de Cornulitidae (incertae sedis) provenant du Devonien du Massif armoricain (rade de Brest, Formation de Kerdreolet, Emsien superieur, zone a patulus) est decrite. Reticornulites reticulatus n. gen., n. sp., preserve a laetat daempreintes et de moules internes, est principalement caracterise par une coquille conique, courbe et flexueuse, apparemment libre daattache, pourvue daune ornementation treillissee a anneaux transversaux dominants. La structure et la microstructure de la coquille demeurent inconnues.