Below are photos of the moon snails we study in Veracruz, Panama. Their shells tend to be quite variable and are sometimes hard to use to determine species. The family is Naticidae, and right now I think the genus is Natica, but it could be Polinices... well, have a look for yourself!
View of the operculum, funicle, and umbilicus. Is the operculum calcareous?
Some physical characteristics used for diagnosis include:
Figures from Poutiers' Gastropods.
Aperture - principle opening.
Callus - thick secondary deposit of lime, generally shiny and porcellaneous.
Columella - coiling axis of shell, forming the anterior part of inner lip.
Funicle - a ridge of callus spiraling into the umbilicus in the naticids.
Operculum - horny or calcareous part attached to the foot; it seals the aperture when the animal withdraws
into the shell.
Umbilicus - opening at base of shell made around the coiling axis when columella is hollow.
Example Natica shell from Bulletins of American Paleontology compared with our shell.
1. Keen, Myra A. 1958. Sea Shells of Tropical West America. Stanford University Press, Standford, California.
2. Poutiers, J.M. Gastropods.
3. Bulletins of American paleontology. Ithaca, N.Y.,Paleontological Research Institution.
v.70, no.292-294 (1976-1977): http://www.biodiversitylibrary.org/item/40502
Page(s): Plate 36, Page 475, Expl. of Plate 36