The enigmatic genus Pseudohercostomus Stackelberg, 1931, considered incertae sedis, is characterised by a very wide metepimeron, and tarsomeres 1–4 of the mid and hind legs entirely set with anterodorsal transverse comb-like rows of bristles. The genus is reported for the first time from Singapore and Pseudohercostomus singaporensis, new species, is described from a swamp forest in Kranji Marshes. The species is also newly recorded from Cambodia. The new species is compared with P. echinatus Stackelberg, 1931, the type species of the genus that was described from Java, Indonesia. The Afrotropical species formerly reported as P. echinatus seems to belong to a different species and is described here as P. congoensis, new species. It is recorded from DR Congo and Mozambique. Hence, the presence of P. echinatus in the Afrotropical Region is considered doubtful. A key is provided for the five species actually considered to belong to Pseudohercostomus.

There is relatively little documentation on fungal decay in tropical trees in general. While the identity of the fungus is unconfirmed, its fruiting body appears similar to the genus Ganoderma, a group comprising mostly fungi that grow on logs (living or dead) with a preference for feeding on lignin in wood (Corner, 1983; Wijedasa, 2013). In the present observation, we record a species of fungus which has digested the wood of Melaleuca cajuputi, causing a distinctive pattern of white decayed wood with black lines, which in future, may assist in the identification of this species of fungus in trees.

The Indochinese freshwater pearl mussel Gibbosula laosensis is a little-known but endangered species with a disjunctive range in the Mekong and Sittaung drainage basins. Here we provide an overview of two taxonomic names, i.e., Unio sella and U. sula that were linked to Gibbosula laosensis. We show that the name Unio sella has been introduced by Cesare Maria Tapparone-Canefri on the labels of at least two shell lots, which were collected by Leonardo Fea during his travel to the Karen Hills in British Burma in the years 1887–1888. However, Tapparone-Canefri did not publish this name for unknown reasons. Fritz Haas mentioned this name in the year 1912 as an unpublished name and a synonym of Gibbosula laosensis based on a study of two specimens of the latter species from the Natural History Museum Vienna (NHMW). Ten years later, Baini Prashad also provided a description of what he accepted as Unio sella, but he used a series of four shells from the Museo Civico di Storia Naturale di Genova (MSNG) that contained two specimens of Yaukthwa nesemanni and two specimens of Gibbosula laosensis. Prashad followed the handwritten labels of Tapparone-Canefri and considered the sample of the first species as young specimens of Unio sella, while Gibbosula laosensis specimens have been treated by him as adult shells of this taxon. To retain the concept of Unio sella published by Prashad, we designate a specimen of Yaukthwa nesemanni that was among Tapparone-Canefri’s series in MSNG to be the lectotype of U. sella Prashad, 1922. Hence, there are two different taxa under the name Unio sella, i.e., U. sella Haas, 1912, a synonym of Gibbosula laosensis (Margaritiferidae: Gibbosulinae), and U. sella Prashad, 1922, a primary junior homonym of Haas’s taxon and a senior synonym of Yaukthwa nesemanni (Unionidae: Rectidentinae). However, in both cases this name is initially unavailable, because it was introduced as a synonym and was never used as a valid name (Art. 11.6 of the International Code of Zoological Nomenclature). Finally, the name Unio sula Simpson, 1900 nom. nudum seems to have originated through an incorrect spelling of U. sella Prashad, 1922 because “sella” is written like “sula” on the original label of Yaukthwa nesemanni sample in MSNG.

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