These can be formed by taking a normal singularity and adding some lower degree terms.

## A1-- |

A1-- x^2-y^2-z^2 |

Hyperboloid of 1 sheet x^2-y^2-z^2 =-0.1 |

Hyperboloid of 2 sheet x^2-y^2-z^2 =+0.1 |

## D4-- |

D4-- x^2 y-y^3-z^2 |

One A3 x^2 y-y^3-z^2 - a x^2 |

3 A1 x^2 y-y^3-z^2 - a(x^2-y^2) |

3 A1 x^2 y-y^3-z^2 + a(x^2-y^2) |

## Three Planes |

Three planes x y z=0 |

Two crosscaps (Crosscap propeller)
x y z + a(x^2+y^2)=0 |

Cone and a plane x y z + x^3 |