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Phenacostethus sikat, new species, is described from coastal drainages of Kalimantan Selatan, the southeastern province of Indonesian Borneo, that flow into the Java Sea and the Straits of Makassar. This discovery and description brings the number of valid species of priapiumfishes, the atheriniform subfamily Phallostethinae, to 24 and extends the known distribution of the phallostethines to drainages on the eastern margin of the modern Sunda Shelf. Phenacostethus sikat differs from congeners in features of the priapium, the complex bilaterally asymmetric, subcephalic copulatory organ of males, and is readily distinguished by a unique, brush-shaped seminal papilla in males, as opposed to a simpler, ruffled seminal papilla in Phe. smithi, its inferred sister species based on morphology, and a smooth seminal papilla in males of Phe. posthon and Phe. trewavasae. Males of Phe. sikat and Phe. smithi are either sinistral or dextral, the hooked toxactinium arises on the right or left side of the head and curves strongly under the head towards the aproctal side of the body. Males of Phe. posthon and Phe. trewavasae are exclusively dextral or sinistral, respectively. Males of Phe. sikat have an ossified inner pulvinular bone which is cartilaginous or absent in Phe. smithi. Males of Phe. sikat and Phe. smithi have a curved and pointed or blunt second ctenactinium as opposed to a highly reduced second ctenactinium in males of Phe. posthon and Phe. trewavasae. Females of the new species lack rudimentary pelvic fins which are present in adult females of Phe. smithi, Phe. posthon, and Phallostethus. The new species is also diagnosed by a colour pattern with few or no melanophores along the horizontal septum anterior to the anal-fin origin. The mtCOI sequences of Phe. sikat differ from those of congeners by 13.85-24.23%, with an average of 21.54%, an extraordinarily high level of divergence comparable to that of other diminutive fishes. Like congeners, Phe. sikat is a miniature species. The largest specimen known is an adult female just 15.3 mm SL. [ABSTRACT FROM AUTHOR]

A new cassid species of the genus Phalium Link, 1807 is described from material trawled in the Sunda Shelf. Phalium pseudobandatum, new species, is superficially close to P. bandatum (Perry, 1811) because of similarities in shell colour and markings. However, the new species can be separated from P. bandatum by conchological characteristics. The position of the posterior sinus in the new species is at or extends above the shoulder, accompanied by a low spire with a side profile that is smooth and not step-like. It also has a less rotund body whorl with a more angular shoulder compared to P. bandatum. A distinct groove on the parietal shield where it adjoins the body whorl is also present on shells of the new species. In addition, the thickened middle part of the outer lip is not seen in similarly sized specimens of P. bandatum. The siphonal canal of the new species is not pigmented, and the crenulations at the anterior edge of the outer lip are more numerous but less distinct than in P. bandatum. We also suggest that P. exaratum (Reeve, 1848) is a distinct Indian Ocean species rather than a geographical subspecies of P. bandatum. [ABSTRACT FROM AUTHOR]