Conical Spiral
A surface modeled after the shape of a Seashell. One parameterization (left figure) is given by
 |  |  | (1) |
 | |  | (2) |
 | |  | (3) |
where
, and 
(Wolfram). Nordstrand gives the parameterization | |  | (4) |
| |  | (5) |
| |  | (6) |
for
(right figure with 
, 
, 
, and 
).
References
Gray, A. ``Sea Shells.'' §11.6 in Modern Differential Geometry of Curves and Surfaces. Boca Raton, FL: CRC Press, pp. 223-223, 1993. Nordstrand, T. ``Conic Spiral or Seashell.'' http://www.uib.no/people/nfytn/shelltxt.htm.
Wolfram Research ``Mathematica Version 2.0 Graphics Gallery.''http://www.mathsource.com/cgi-bin/MathSource/Applications/Graphics/3D/0207-155.
- Hecke Ring
- Hectogon
- Hedgehog
- Heegaard Diagram
- Heegaard Splitting
- Heegner Number
- Heesch Number
- Heesch's Problem
- Height
- Heilbronn Triangle Problem
- Heine-Borel Theorem
- Heine Hypergeometric Series
- Heisenberg Group
- Heisenberg Space
- Held Group
- Helen of Geometers
- Helicoid
- Helix
- Helly Number
- Helly's Theorem
- Helmholtz Differential Equation
- Helmholtz Differential Equation--Bipolar Coordinates
- Helmholtz Differential Equation--Cartesian Coordinates
- Helmholtz Differential Equation--Circular Cylindrical Coordinates
- Helmholtz Differential Equation--Confocal Ellipsoidal Coordinates