in combination = Concavely, concave and —, as in Concavo-concave, concave on both sides; Concavo-convex, concave on one side and convex on the other, and thinnest in the center.
1675. Boyle, New Exp., II., in Phil. Trans., XI. 800. The two surfaces of it gave it some resemblance in point of shape … to a Concavo-Convex Glass.
1727–51. Chambers, Cycl., s.v., Concave, Lenses … concave on one side, and convex on the other, called concavo-convex, or convexo-concave, as the one or the other surface is a portion of a less sphere.
1831. Brewster, Optics, iv. 27. A concavo-convex lens … is a lens one of whose surfaces is concave and the other convex, and in which the two surfaces will not meet though continued.
1858. Geikie, Hist. Boulder, vi. 98. Both the valves are concavo-convex, or arched in the same direction like two saucers … within each other.
