conchoid | Dürer shell curve | muschellini

y^2 (b^2 - 3 a^2) + a^2 (a^2 - b^2) + 2 a^2 b (x + y) - a^2 x^2 - 2 b y^2 (x + y) + 2 y^2 (x^2 + y^2) = 0

algebraic | conchoid | quartic

d = 4