Lewis & Short

con-vallis, is (abl. regularly convalle, e. g. Caes. B. G. 3, 20 fin.; Liv. 1, 12, 10; Verg. G. 2, 186; id. A. 6, 679 al.: convalli, Varr. R. R. 1, 12, 3; gen. plur. convallium, Plin. 36, 15, 23, § 100). f. (plur. post-class. access. form convallia, ium, n., sc. loca, Prud. στεφ. 10, 331 al.), a valley enclosed on all sides; cf. Paul. ex Fest. p. 42, 6 Müll.; Varr. L. L. 5, § 20 ib. (freq. and class. in prose and poetry); Lucr. 5, 1374; Cic. Agr. 2, 35, 96; Caes. B. G. 5, 32; Liv. 1, 38, 6; Verg. G. 3, 276; Juv. 16, 36 et saep.