C. abruptus (Otaian-Altonian, Pakaurangi) also has a very depressed spire, but it is more slender than C. trigonicus and has far less prominent and less ubiquitous spiral sculpture.
Scratchpads developed and conceived by (alphabetical):
Ed Baker,
Katherine Bouton
Alice Heaton
Dimitris Koureas,
Laurence Livermore,
Dave Roberts,
Simon Rycroft,
Ben Scott,
Vince Smith