The lens has an ellipsoid, biconvex shape. The shell is typically impunctate, biconvex, and oval or subcircular in shape. The fruit is an oval, slightly biconvex box. A lens is "biconvex" (or "double convex", or just "convex") if both surfaces are convex. It has rigid, terete and biconvex culms that are smooth and glabrous. In shape they are sub-circular to elliptical, with typically biconvex valves. The lens then increases its curvature to become more biconvex, thus increasing refractive power. The 1589 second edition added a "lenticular crystal" or biconvex lens to the setup. It has two biconvex lens on the outer and a biconcave lens in the middle. Extensions of convex optimization include the optimization of biconvex, pseudo-convex, and quasiconvex functions. The vertebra features a biconvex centrum, a feature shared with other titanosaurs. Terebratulids typically have biconvex shells that are usually ovoid to circular in outline.