The rather smooth bright green turbans, 50 to 80 mm, which are found in bins
and baskets in tourist shops are acid-cleaned Turbo argyrostomus. The
unnatural color is due to the acid cleaning (as is the smooth feel of the
shells). The small (1 to 1-1/4 inches) turbans that are frequently found in
craft mixes, etc. may of course include juvenile T. argyrostomus, but many
of them are Turbo stenogyrus Fischer, 1873. This is superficially similar to
T. argyrostomus, but is consistently smaller, more angular in outline, has
mostly finer cords but with a few larger raised cords, and is much more
variable in color than T. argyrostomus. It can be cream to tan to brown to
greenish, with markings in white, green, black, and sometimes red. This is
abundant in Japan and Taiwan, and is exported by the ton for craft purposes.

Regards,
Paul M.

Several specimens can be seen here:
http://www.petdiscounters.com/small_animal/reptile/hermit/zz_shell_green_tur
bo_stenogyrus.html