Wallis conical edge
Wallis's conical edge is a ruled surface given by the parametric equations. In geometry, a surface S is ruled if through every point of S there is a straight line that lies on S. The most familiar examples are the plane and the curved surface of a cylinder or cone. Wallis's conical edge is also a kind of right conoid. In geometry, a right conoid is a ruled surface generated by a family of straight lines that all intersect perpendicularly a fixed straight line, called the axis of the right conoid.