Key to the Opisthostoma species from Java

1a. Aperture pointing backwards or tilted up to 45 degrees, teleoconch coarsely and widely ribbed (19–35 ribs on the penultimate whorl).................................................................................... O. javanicum

1b. Aperture pointing to the upper side, teleoconch finer and more closely ribbed.................................... 2

2a. Shell oblique cylindrical, more coarsely ribbed, peristome distinctly expanded....................... O. uranoscopium

2b. Shell depressed, more finely ribbed, peristome not so strongly expanded........................... Opisthostoma sp.