Shape of the Spire

sh = spire height
sd = spire diameter
sl = shell lenght
ah = aperture height

Absolute Height of Spire
ASH = sh/sd

Relative Height of Spire
RSH = sl-ah/sl


Low to sunken RSH ≤ 0.10 ASH ≤ 0.20 augur	Moderately low 0.11 ≤ RSH ≤ 0.15 0.21 ≤ ASH ≤ 0.30 ferrugineus	Moderate 0.16 ≤ RSH < 0.20 0.31 ≤ ASH < 0.40 achatinus

Moderately hight 0.21 ≤ RSH ≤ 0.25 0.41 ≤ ASH ≤ 0.50 fulmen	Hight 0.26 ≤ RSH ≤ 0.30 0.51 ≤ ASH ≤ 0.70 pagodus	Very Hight RSH > 0.30 ASH > 0.70 excelsus