convexĭtas, ātis, f. [convexus],
a vaulting, convex roundness, convexity, concavity (postAug.; perh. only in Plin. the elder): circuli, Plin. 18, 25, 57, § 217: mundi, id. 18, 25, 57, § 210: cava in caelo, id. 2, 64, 64, § 160: terrae, id. 18, 29, 69, § 283: insulae, id. 6, 32, 37, § 202.