OK, apparently there are at least 2 селa named Межиріч in Ukraine. Ukiewiki has an article on both the archaeological site as well supposed culture which created it:  Межиріцька культура. Given that Ukiewiki believes that this Межиріч is located in Cherkasy Oblast, as well as the coordinates 49 deg 38' N, 31 deg 24'E given in one of the online sources I linked to in the article, which are different than the coordinates in the Shtetlink page for a shtetl in Ekaterinoslav, I am going to assume it's not the Межиріч in the Dnipropetrovsk Oblast. 

Thankfully, I have information on the Cherkasy Oblast at home.