Transversa is often found where domingensis is found - Under rocks, in cracks and crevices.  However, domingensis is not found among grasses and sandy bottoms where transversa can also be found.

The two are similar when viewed separately, but obviously different when compared side-by-side.  Domingensis is more bulbous, has more, narrower ribs, and the ventral lips match up tightly.  Transversa is readily differentiated by the larger, overlapping left valve.