I mentioned in my last post that terrestrial snails are difficult to study because of the lack of good field guides. That is only part of the problem. Another issue is the names. You key out a snail from a field guide printed in the 1940s and from one in the 1960s and you will get different names. Plug the names into Natureserve Explorer and you will find something different.
That is to be expected. But some snails that are obviously different have similar (or identical) species names.
One case in point: In Iowa we have a snail called Hendersonia occulta. This is a fairly famous snail, belonging to a different group of snails than the rest of Iowa’s terrestrial snails. I don’t have any photos of it ( but I think M.J. Hatfield gave me a shell–I need to find it and photograph it). Normally when scientific names are changed the genus name changes but the species name stays the same.
We also have a snail named Vertigo occulta. At least I think we do. I can’t find any mention of it in the scientific literature, but it is listed as threatened on Iowa’s T. & E. species list. Same species name, very different snails (if there is actually a V. occulta)
We also have Heliodiscus shimeki and Discus shimekii, named after an Iowa botanist and malacologist.
I think this snail and the snail on the bottom photo of my last post is D. shimekii. I am not sure but I think they were the same individual–they were at least taken at the same time and location.
Two snails with species names that are similar, but not identical.