Pulau Kapas might be covered in Amphidromus inversus, but that isn't the only snail on the island. This is an unknown species of succineid (I think).
Succineidae has a worldwide distribution. In Europe and North America, the family is associated with marshes and swamps, but elsewhere the snails might occur in any habitat. I found this Malaysian snail in rainforest. Australian succineids live in coastal heath, under eucalypt bark and on sand dunes. Tough little beggars.
They're difficult to identify. The shells all look pretty much the same (a few rapidly expanding whorls, no markings), as does the internal anatomy. There's nothing fancy about these snails.
So it's down to DNA to sort them out. Dr Rob Cowie and colleagues at the University of Hawaii are doing just that. They've already looked at thirteen species of Hawaiian succineids and found that the current taxonomic arrangement is all over the place like a mad woman's knitting. Almost everything is shoved into the open drawer marked Succinea, whether it should be there or not. Still, in which generic drawers those species should really go remains conjecture—until someone does a full-scale study of the family.
In the meantime, I've got no idea what species this is. If you can put a name on it, please let me in on the secret.
Rundell, R.J., Holland, B.S. & Cowie, R.H. (2004). Molecular phylogeography of the endemic Hawaiian Succineidae (Gastropoda: Pulmonata). Molecular Phylogenetics and Evolution 31: 246-255.