Salt-marsh foraminiferal assemblages serve as a key proxy for reconstructing sea level on multi-decadal to multi-millennial timescales, enabling reconstruction of sea level to potentially within 5 to 15-cm precision. The genus Trochamminita, common in salt-marsh environments, has proven unclear in recent decades with regard to the number of species represented within it. Because different species may possess different preferred elevations relative to sea level, it is important that the number of taxa be elucidated, to ensure future sea-level reconstructions using foraminifera are as precise as possible. Here, using new specimens identified from Pauatahanui Inlet, southern North Island of New Zealand, and Aramoana salt marsh, southern South Island, the agglutinated species Trochamminita irregularis is recognised as likely distinct from Trochamminita salsa, and a new species, Pseudotrochamminita malcolmi (n. gen., n. sp.), is named, having been identified in earlier studies either as specimens of T. irregularis, or of the unrelated species Polysaccammina ipohalina. Trochamminita irregularis and Ps. malcolmi differ from one another in chamber morphology, apertural morphology and number, chamber texture, geographical distribution, and optimal heights relative to sea level.