Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Carmentis, is (Carmenta, ae, Liv. 1, 7, 8 Weissenb. ad loc.; Hyg. Fab. 277), f. [carmen, q. v.], a Roman goddess of prophecy, acc. to mythologists, the mother of Evander, who went with him from Arcadia to Latium (hence Arcadia dea, Ov. F. 1, 462: Parrhasia dea, id. ib. 1, 618: Tegeaea parens, id. ib. 1, 627: Tegeaea sacerdos, id. ib. 6, 531, and Maenalis nympha, id. ib. 1, 634), and uttered oracles on the Capitoline Hill, Ov. F. 1, 462 sq.; Liv. l. l.; 5, 47, 2; Hyg. Fab. 277; Verg. A. 8, 336 sq., and Serv. ad h. l.
Also represented as two goddesses, Carmentes, and under the especial names Postverta and Prorsa (the backwards and forwards looking goddess), Varr. ap. Gell. 16, 16; Serv. ad Verg. l. l.
Hence,