Asian clam

Ali Hemati Pour, you are very welcome. However, I am not sure I understand the question. C. fluminalis belong in the wilderness right where you find them. They are a normal part of those ecosystems. Was I able to answer your question with that or did I miss?

Ali, I really think this is C. fluminalis, and not C. fluminea. C. fluminalis is native to where you found this shell, and is differentiated by having 15-23 ridges per cm, whereas C. fluminea has 7-14 ridges. And C. fluminea is not known to be introduced to Iran.

This is a species of Corbicula, and I would expect that this is Corbicula fluminalis, the only species of the genus Corbicula listed as being native to Iran. If you have any photos of the interior of the shell, that could help with the ID (though on a specimen this long deceased, maybe not). Here's the link I used to narrow that down: http://www.iucnredlist.org/details/156166/0 It's not as well known or as well studied as C. fluminea (nor is it as widespread and invasive worldwide), but C. fluminalis is still an invasive over much of Europe.