Bicylindrics

Two closed curves obtained as the intersection of two cylinders the axes of which intersect at right angles. The parametric equations of bicylindrics are

$$x=a\cos t,\quad y=\pm\sqrt{b^2-a^2\sin^2t},\quad z=a\sin t,\quad b\geq a,$$

where $a$ and $b$ are the radii of the cylinders and $t$ is a parameter. If $a=b$, the bicylindrics is a pair of congruent ellipses.