 A ridge on the surface corresponds to a cuspidal edges so each sheet of the elliptical focal surface will have three cuspidal edges which come together at the umbilic focus and then switch to the other sheet.For a hyperbolic umbilic there is a single cuspidal edge which switch from one sheet to the other.A point "p" in a Riemannian submanifold is umbilical if, at "p", the (vector-valued) Second fundamental form is some normal vector tensor the induced metric (First fundamental form).